diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 36f94bd..2ac613b 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -32,7 +32,7 @@ jobs:
         run: composer install --prefer-dist --no-progress --no-interaction
 
       - name: Lint
-        run: make fmtcheck
+        run: vendor/bin/php-cs-fixer fix -v --using-cache=no --dry-run
 
   static-analysis:
     name: Static Analysis
@@ -51,7 +51,7 @@ jobs:
         run: composer install --prefer-dist --no-progress --no-interaction
 
       - name: Run PHPStan
-        run: make analyse
+        run: PHPSTAN_DISABLE_PARALLEL=1 vendor/bin/phpstan analyse --configuration=phpstan.neon --no-progress --memory-limit=1G --debug
 
   docs:
     name: Docs
@@ -70,7 +70,7 @@ jobs:
         run: composer install --no-interaction --prefer-dist
 
       - name: Generate docs
-        run: make docs
+        run: docker run --rm -v "$PWD:/data" "phpdoc/phpdoc:3"
 
       - name: Ensure docs are up to date
         run: git diff --exit-code -- docs
diff --git a/.github/workflows/generate.yaml b/.github/workflows/generate.yaml
index 7066b8c..a104948 100644
--- a/.github/workflows/generate.yaml
+++ b/.github/workflows/generate.yaml
@@ -44,7 +44,7 @@ jobs:
         working-directory: codegen
 
       - name: Format
-        run: make fmt
+        run: vendor/bin/php-cs-fixer fix -v --using-cache=no
 
       - name: Create GitHub App token
         id: app-token
diff --git a/Makefile b/Makefile
deleted file mode 100644
index f13a785..0000000
--- a/Makefile
+++ /dev/null
@@ -1,40 +0,0 @@
-# Make this makefile self-documented with target `help`
-.PHONY: help
-.DEFAULT_GOAL := help
-help: ## Show help
-	@grep -Eh '^[0-9a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'
-
-.PHONY: vendor
-vendor: install ## Backward-compatible alias for install
-
-.PHONY: install
-install: composer.json composer.lock ## Install all project dependencies
-	composer install
-
-.PHONY: lock
-lock: ## Update the lockfile
-	composer update --with-all-dependencies
-
-.PHONY: fmt
-fmt: install ## Format code using php-cs-fixer
-	vendor/bin/php-cs-fixer fix -v --using-cache=no
-
-.PHONY: fmtcheck
-fmtcheck: install ## Check code formatting
-	vendor/bin/php-cs-fixer fix -v --using-cache=no --dry-run
-
-.PHONY: docs
-docs: install ## Generate API reference using phpDocumentor
-	docker run --rm -v "$(CURDIR):/data" "phpdoc/phpdoc:3"
-
-.PHONY: test
-test: install ## Run PHPUnit test suite
-	composer test
-
-.PHONY: analyse
-analyse: install ## Run static analysis (PHPStan)
-	PHPSTAN_DISABLE_PARALLEL=1 vendor/bin/phpstan analyse --configuration=phpstan.neon --no-progress --memory-limit=1G --debug
-
-.PHONY: generate
-generate: ## Generate SDK from the local OpenAPI specs
-	cd codegen && go run ./... generate ../openapi.json ../src
diff --git a/README.md b/README.md
index a3f91f5..72fe5aa 100644
--- a/README.md
+++ b/README.md
@@ -37,12 +37,12 @@ try {
     // SDK automatically uses SUMUP_API_KEY environment variable
     $sumup = new \SumUp\SumUp();
 
-    $request = new \SumUp\Types\CheckoutCreateRequest([
-        'amount' => 10.00,
-        'currency' => 'EUR', // or CheckoutCreateRequestCurrency::EUR
-        'checkout_reference' => 'your-checkout-ref',
-        'merchant_code' => 'YOUR-MERCHANT-CODE',
-    ]);
+    $request = new \SumUp\Types\CheckoutCreateRequest(
+        checkoutReference: 'your-checkout-ref',
+        amount: 10.00,
+        currency: 'EUR', // or CheckoutCreateRequestCurrency::EUR
+        merchantCode: 'YOUR-MERCHANT-CODE',
+    );
 
     $checkout = $sumup->checkouts()->create($request);
 
@@ -63,7 +63,7 @@ try {
 }
 ```
 
-Service methods also accept associative arrays as request payloads. For typed usage, prefer DTOs from `\SumUp\Types\...` with `new TypeName([...])`.
+Service methods also accept associative arrays as request payloads. For typed usage, prefer DTOs from `\SumUp\Types\...` with named arguments, or use `TypeName::fromArray([...])` when you already have associative array data.
 
 ### Providing API Key Programmatically
 
diff --git a/codegen/pkg/generator/generator.go b/codegen/pkg/generator/generator.go
index 6d3b2e1..8359be4 100644
--- a/codegen/pkg/generator/generator.go
+++ b/codegen/pkg/generator/generator.go
@@ -53,6 +53,9 @@ type Generator struct {
 
 	// enumNamespaces tracks where an enum is defined so we can reference it.
 	enumNamespaces map[string]string
+
+	// requestClassNames tracks schema classes used as OpenAPI request bodies.
+	requestClassNames map[string]struct{}
 }
 
 type enumDefinition struct {
@@ -67,6 +70,7 @@ func New(cfg Config) *Generator {
 	return &Generator{
 		cfg:               cfg,
 		inlineSchemaNames: make(map[*base.SchemaProxy]string),
+		requestClassNames: make(map[string]struct{}),
 	}
 }
 
@@ -88,6 +92,7 @@ func (g *Generator) Load(spec *v3.Document) error {
 	usage := g.collectSchemaUsage()
 	g.schemasByTag, g.schemaNamespaces = g.assignSchemasToTags(usage)
 	g.operationsByTag = g.collectOperations()
+	g.collectRequestClassNames()
 	g.enumsByTag, g.enumNamespaces = g.collectEnums()
 
 	return nil
@@ -280,32 +285,219 @@ func (g *Generator) buildPHPClass(name string, schema *base.SchemaProxy, current
 		buf.WriteString(propCode)
 	}
 
-	if strings.HasSuffix(name, "Request") && name != "BadRequest" {
-		buf.WriteString(g.buildRequestArrayConstructor(properties))
+	if g.shouldGenerateConstructorForClass(name) {
+		buf.WriteString(g.buildRequestConstructor(properties))
 	}
 
 	buf.WriteString("}\n")
 	return buf.String()
 }
 
-func (g *Generator) buildRequestArrayConstructor(_ []phpProperty) string {
+func (g *Generator) buildRequestConstructor(properties []phpProperty) string {
 	var buf strings.Builder
 
+	buf.WriteString("    /**\n")
+	buf.WriteString("     * Create request DTO.\n")
+	buf.WriteString("     *\n")
+	for _, prop := range constructorProperties(properties) {
+		fmt.Fprintf(&buf, "     * @param %s $%s\n", g.constructorParamDocType(prop), prop.Name)
+	}
+	buf.WriteString("     */\n")
+	buf.WriteString("    public function __construct(")
+	constructorProps := constructorProperties(properties)
+	if len(constructorProps) > 0 {
+		buf.WriteString("\n")
+		for idx, prop := range constructorProps {
+			buf.WriteString("        ")
+			buf.WriteString(g.constructorParamType(prop))
+			buf.WriteString(" $")
+			buf.WriteString(prop.Name)
+			if prop.Optional {
+				buf.WriteString(" = null")
+			}
+			if idx < len(constructorProps)-1 {
+				buf.WriteString(",")
+			}
+			buf.WriteString("\n")
+		}
+		buf.WriteString("    ")
+	}
+	buf.WriteString(") {\n")
+	buf.WriteString("        \\SumUp\\Hydrator::hydrate([\n")
+	for _, prop := range constructorProps {
+		fmt.Fprintf(&buf, "            '%s' => $%s,\n", prop.SerializedName, prop.Name)
+	}
+	buf.WriteString("        ], self::class, $this);\n")
+	buf.WriteString("    }\n\n")
+
 	buf.WriteString("    /**\n")
 	buf.WriteString("     * Create request DTO from an associative array.\n")
 	buf.WriteString("     *\n")
 	buf.WriteString("     * @param array<string, mixed> $data\n")
 	buf.WriteString("     */\n")
-	buf.WriteString("    public function __construct(array $data = [])\n")
+	buf.WriteString("    public static function fromArray(array $data): self\n")
 	buf.WriteString("    {\n")
-	buf.WriteString("        if ($data !== []) {\n")
-	buf.WriteString("            \\SumUp\\Hydrator::hydrate($data, self::class, $this);\n")
-	buf.WriteString("        }\n")
+	requiredProps := requiredProperties(properties)
+	if len(requiredProps) > 0 {
+		buf.WriteString("        self::assertRequiredFields($data, [\n")
+		for _, prop := range requiredProps {
+			fmt.Fprintf(&buf, "            '%s' => '%s',\n", prop.SerializedName, prop.Name)
+		}
+		buf.WriteString("        ]);\n\n")
+	}
+	buf.WriteString("        $request = (new \\ReflectionClass(self::class))->newInstanceWithoutConstructor();\n")
+	buf.WriteString("        \\SumUp\\Hydrator::hydrate($data, self::class, $request);\n\n")
+	buf.WriteString("        return $request;\n")
 	buf.WriteString("    }\n\n")
 
+	if len(requiredProps) > 0 {
+		buf.WriteString("    /**\n")
+		buf.WriteString("     * @param array<string, mixed> $data\n")
+		buf.WriteString("     * @param array<string, string> $requiredFields\n")
+		buf.WriteString("     */\n")
+		buf.WriteString("    private static function assertRequiredFields(array $data, array $requiredFields): void\n")
+		buf.WriteString("    {\n")
+		buf.WriteString("        foreach ($requiredFields as $serializedName => $propertyName) {\n")
+		buf.WriteString("            if (!array_key_exists($serializedName, $data) && !array_key_exists($propertyName, $data)) {\n")
+		buf.WriteString("                throw new \\InvalidArgumentException(sprintf('Missing required field \"%s\".', $serializedName));\n")
+		buf.WriteString("            }\n")
+		buf.WriteString("        }\n")
+		buf.WriteString("    }\n\n")
+	}
+
 	return buf.String()
 }
 
+func constructorProperties(properties []phpProperty) []phpProperty {
+	result := make([]phpProperty, 0, len(properties))
+	for _, prop := range properties {
+		if !prop.Optional {
+			result = append(result, prop)
+		}
+	}
+	for _, prop := range properties {
+		if prop.Optional {
+			result = append(result, prop)
+		}
+	}
+	return result
+}
+
+func requiredProperties(properties []phpProperty) []phpProperty {
+	result := make([]phpProperty, 0, len(properties))
+	for _, prop := range properties {
+		if !prop.Optional {
+			result = append(result, prop)
+		}
+	}
+	return result
+}
+
+func (g *Generator) constructorParamDocType(prop phpProperty) string {
+	docType := prop.DocType
+	if docType == "" {
+		docType = "mixed"
+	}
+	if backingType := g.enumBackingType(prop.Type); backingType != "" {
+		docType += "|" + backingType
+	}
+	if prop.Optional && !strings.Contains(docType, "null") {
+		docType += "|null"
+	}
+	return docType
+}
+
+func (g *Generator) constructorParamType(prop phpProperty) string {
+	paramType := prop.Type
+	if paramType == "" {
+		paramType = "mixed"
+	}
+
+	if backingType := g.enumBackingType(paramType); backingType != "" {
+		paramType += "|" + backingType
+	}
+
+	if prop.Optional && paramType != "mixed" {
+		if strings.Contains(paramType, "|") {
+			if !strings.Contains(paramType, "null") {
+				paramType += "|null"
+			}
+		} else if !strings.HasPrefix(paramType, "?") {
+			paramType = "?" + paramType
+		}
+	}
+
+	return paramType
+}
+
+func (g *Generator) enumBackingType(typeName string) string {
+	if typeName == "" {
+		return ""
+	}
+
+	trimmed := strings.TrimPrefix(typeName, "\\")
+	parts := strings.Split(trimmed, "\\")
+	enumName := parts[len(parts)-1]
+	if enumName == "" {
+		return ""
+	}
+
+	for _, enums := range g.enumsByTag {
+		for _, enum := range enums {
+			if enum.Name == enumName {
+				return enum.Type
+			}
+		}
+	}
+
+	return ""
+}
+
+func (g *Generator) collectRequestClassNames() {
+	g.requestClassNames = make(map[string]struct{})
+	for _, operations := range g.operationsByTag {
+		for _, op := range operations {
+			if op == nil || !op.HasBody || op.BodyType == "" {
+				continue
+			}
+			className := phpClassBaseName(op.BodyType)
+			if className == "" || isBuiltinPHPType(className) {
+				continue
+			}
+			g.requestClassNames[className] = struct{}{}
+		}
+	}
+}
+
+func (g *Generator) shouldGenerateConstructorForClass(className string) bool {
+	if className == "" || className == "BadRequest" {
+		return false
+	}
+	if strings.HasSuffix(className, "Request") {
+		return true
+	}
+	_, ok := g.requestClassNames[className]
+	return ok
+}
+
+func phpClassBaseName(typeName string) string {
+	trimmed := strings.TrimPrefix(typeName, "\\")
+	if strings.Contains(trimmed, "|") {
+		return ""
+	}
+	parts := strings.Split(trimmed, "\\")
+	return parts[len(parts)-1]
+}
+
+func isBuiltinPHPType(typeName string) bool {
+	switch typeName {
+	case "array", "mixed", "string", "int", "float", "bool", "null", "void":
+		return true
+	default:
+		return false
+	}
+}
+
 func (g *Generator) displayTagName(tagKey string) string {
 	if tagKey == sharedTagKey {
 		return sharedTagDisplayName
diff --git a/codegen/pkg/generator/services.go b/codegen/pkg/generator/services.go
index 449561b..892027c 100644
--- a/codegen/pkg/generator/services.go
+++ b/codegen/pkg/generator/services.go
@@ -286,10 +286,10 @@ func (g *Generator) renderServiceMethod(serviceClass string, op *operation) stri
 	buf.WriteString("        $payload = [];\n")
 	if op.HasBody {
 		if op.BodyRequired {
-			buf.WriteString("        $payload = RequestEncoder::encode($body);\n")
+			buf.WriteString(g.renderBodyEncoding("$body", op.BodyType, "        "))
 		} else {
 			buf.WriteString("        if ($body !== null) {\n")
-			buf.WriteString("            $payload = RequestEncoder::encode($body);\n")
+			buf.WriteString(g.renderBodyEncoding("$body", op.BodyType, "            "))
 			buf.WriteString("        }\n")
 		}
 	}
@@ -459,7 +459,17 @@ func shouldGenerateRequestBodyClass(op *operation) bool {
 func buildEmptyRequestBodyClass(className string) string {
 	var buf strings.Builder
 	fmt.Fprintf(&buf, "/**\n * Request payload for %s.\n *\n * @package SumUp\\Services\n */\n", className)
-	fmt.Fprintf(&buf, "class %s\n{\n}\n", className)
+	fmt.Fprintf(&buf, "class %s\n{\n", className)
+	buf.WriteString("    /**\n")
+	buf.WriteString("     * Create request DTO from an associative array.\n")
+	buf.WriteString("     *\n")
+	buf.WriteString("     * @param array<string, mixed> $data\n")
+	buf.WriteString("     */\n")
+	buf.WriteString("    public static function fromArray(array $data): self\n")
+	buf.WriteString("    {\n")
+	buf.WriteString("        return new self();\n")
+	buf.WriteString("    }\n")
+	buf.WriteString("}\n")
 	return buf.String()
 }
 
@@ -862,6 +872,36 @@ func renderBodyArgument(op *operation) string {
 	return fmt.Sprintf("%s $body", baseType)
 }
 
+func (g *Generator) renderBodyEncoding(bodyExpr string, bodyType string, indent string) string {
+	var buf strings.Builder
+
+	if g.bodyTypeHasGeneratedFromArray(bodyType) {
+		classRef := formatClassReference(bodyType)
+		fmt.Fprintf(&buf, "%s$requestBody = %s;\n", indent, bodyExpr)
+		fmt.Fprintf(&buf, "%sif (is_array($requestBody)) {\n", indent)
+		fmt.Fprintf(&buf, "%s    $requestBody = %s::fromArray($requestBody);\n", indent, classRef)
+		fmt.Fprintf(&buf, "%s}\n", indent)
+		fmt.Fprintf(&buf, "%s$payload = RequestEncoder::encode($requestBody);\n", indent)
+		return buf.String()
+	}
+
+	fmt.Fprintf(&buf, "%s$payload = RequestEncoder::encode(%s);\n", indent, bodyExpr)
+	return buf.String()
+}
+
+func (g *Generator) bodyTypeHasGeneratedFromArray(typeName string) bool {
+	if !bodyTypeAllowsArray(typeName) {
+		return false
+	}
+
+	className := phpClassBaseName(typeName)
+	if className == "" {
+		return false
+	}
+
+	return g.shouldGenerateConstructorForClass(className)
+}
+
 func bodyTypeAllowsArray(typeName string) bool {
 	if typeName == "" {
 		return false
diff --git a/examples/checkout.php b/examples/checkout.php
index ab5941d..75bf9d3 100644
--- a/examples/checkout.php
+++ b/examples/checkout.php
@@ -26,12 +26,12 @@
 $sumup = new \SumUp\SumUp($apiKey);
 
 try {
-    $checkout = $sumup->checkouts()->create(new \SumUp\Types\CheckoutCreateRequest([
-        'amount' => 12.30,
-        'checkout_reference' => 'TX-' . time(),
-        'currency' => 'EUR',
-        'merchant_code' => $merchantCode,
-    ]));
+    $checkout = $sumup->checkouts()->create(new \SumUp\Types\CheckoutCreateRequest(
+        checkoutReference: 'TX-' . time(),
+        amount: 12.30,
+        currency: 'EUR',
+        merchantCode: $merchantCode,
+    ));
 
     if ($checkout->id === null) {
         fwrite(STDERR, "Checkout was created, but response did not include an ID.\n");
diff --git a/examples/oauth2/README.md b/examples/oauth2/README.md
index 370f1f1..81f298b 100644
--- a/examples/oauth2/README.md
+++ b/examples/oauth2/README.md
@@ -86,11 +86,12 @@ $sumup = new \SumUp\SumUp();
 $sumup->setDefaultAccessToken($accessToken);
 
 // Use the SDK normally
-$request = new \SumUp\Types\CheckoutCreateRequest();
-$request->amount = 10.00;
-$request->currency = \SumUp\Types\CheckoutCreateRequestCurrency::EUR;
-$request->checkoutReference = 'order-123';
-$request->merchantCode = $merchantCode;
+$request = new \SumUp\Types\CheckoutCreateRequest(
+    checkoutReference: 'order-123',
+    amount: 10.00,
+    currency: \SumUp\Types\CheckoutCreateRequestCurrency::EUR,
+    merchantCode: $merchantCode,
+);
 
 $checkout = $sumup->checkouts()->create($request);
 ```
diff --git a/justfile b/justfile
new file mode 100644
index 0000000..4ad2647
--- /dev/null
+++ b/justfile
@@ -0,0 +1,43 @@
+set shell := ["bash", "-eu", "-o", "pipefail", "-c"]
+
+# List available recipes. This is the default target.
+default: help
+
+# Display all documented targets.
+help:
+  @just --list
+
+# Backward-compatible alias for installing project dependencies.
+vendor: install
+
+# Install all project dependencies.
+install:
+  composer install
+
+# Update the Composer lockfile.
+lock:
+  composer update --with-all-dependencies
+
+# Format code using php-cs-fixer.
+fmt: install
+  vendor/bin/php-cs-fixer fix -v --using-cache=no
+
+# Check code formatting.
+fmtcheck: install
+  vendor/bin/php-cs-fixer fix -v --using-cache=no --dry-run
+
+# Generate API reference using phpDocumentor.
+docs: install
+  docker run --rm -v "$PWD:/data" "phpdoc/phpdoc:3"
+
+# Run PHPUnit test suite.
+test: install
+  composer test
+
+# Run static analysis using PHPStan.
+analyse: install
+  PHPSTAN_DISABLE_PARALLEL=1 vendor/bin/phpstan analyse --configuration=phpstan.neon --no-progress --memory-limit=1G --debug
+
+# Generate SDK from the local OpenAPI specs.
+generate:
+  cd codegen && go run ./... generate ../openapi.json ../src
diff --git a/src/Checkouts/Checkouts.php b/src/Checkouts/Checkouts.php
index e4b9f8f..31eb568 100644
--- a/src/Checkouts/Checkouts.php
+++ b/src/Checkouts/Checkouts.php
@@ -28,15 +28,50 @@ class CheckoutsCreateApplePaySessionRequest
      */
     public string $target;
 
+    /**
+     * Create request DTO.
+     *
+     * @param string $context
+     * @param string $target
+     */
+    public function __construct(
+        string $context,
+        string $target
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'context' => $context,
+            'target' => $target,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
+        self::assertRequiredFields($data, [
+            'context' => 'context',
+            'target' => 'target',
+        ]);
+
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
+    }
+
+    /**
+     * @param array<string, mixed> $data
+     * @param array<string, string> $requiredFields
+     */
+    private static function assertRequiredFields(array $data, array $requiredFields): void
+    {
+        foreach ($requiredFields as $serializedName => $propertyName) {
+            if (!array_key_exists($serializedName, $data) && !array_key_exists($propertyName, $data)) {
+                throw new \InvalidArgumentException(sprintf('Missing required field "%s".', $serializedName));
+            }
         }
     }
 
@@ -166,7 +201,11 @@ public function create(\SumUp\Types\CheckoutCreateRequest|array $body, ?RequestO
     {
         $path = '/v0.1/checkouts';
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = \SumUp\Types\CheckoutCreateRequest::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
@@ -201,7 +240,11 @@ public function createApplePaySession(string $id, CheckoutsCreateApplePaySession
         $path = sprintf('/v0.2/checkouts/%s/apple-pay-session', rawurlencode((string) $id));
         $payload = [];
         if ($body !== null) {
-            $payload = RequestEncoder::encode($body);
+            $requestBody = $body;
+            if (is_array($requestBody)) {
+                $requestBody = CheckoutsCreateApplePaySessionRequest::fromArray($requestBody);
+            }
+            $payload = RequestEncoder::encode($requestBody);
         }
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
@@ -375,7 +418,11 @@ public function process(string $id, \SumUp\Types\ProcessCheckout|array $body, ?R
     {
         $path = sprintf('/v0.1/checkouts/%s', rawurlencode((string) $id));
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = \SumUp\Types\ProcessCheckout::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
diff --git a/src/Customers/Customers.php b/src/Customers/Customers.php
index 6485ed0..3498f69 100644
--- a/src/Customers/Customers.php
+++ b/src/Customers/Customers.php
@@ -21,16 +21,30 @@ class CustomersUpdateRequest
      */
     public ?\SumUp\Types\PersonalDetails $personalDetails = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param \SumUp\Types\PersonalDetails|null $personalDetails
+     */
+    public function __construct(
+        ?\SumUp\Types\PersonalDetails $personalDetails = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'personal_details' => $personalDetails,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
-        }
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
     }
 
 }
@@ -90,7 +104,11 @@ public function create(\SumUp\Types\Customer|array $body, ?RequestOptions $reque
     {
         $path = '/v0.1/customers';
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = \SumUp\Types\Customer::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
@@ -217,7 +235,11 @@ public function update(string $customerId, CustomersUpdateRequest|array $body, ?
     {
         $path = sprintf('/v0.1/customers/%s', rawurlencode((string) $customerId));
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = CustomersUpdateRequest::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
diff --git a/src/Hydrator.php b/src/Hydrator.php
index 48c261b..b30b9a3 100644
--- a/src/Hydrator.php
+++ b/src/Hydrator.php
@@ -41,7 +41,9 @@ public static function hydrate($payload, $className, $target = null)
             return $payload;
         }
 
-        $object = ($target instanceof $className) ? $target : new $className();
+        $object = ($target instanceof $className)
+            ? $target
+            : (new ReflectionClass($className))->newInstanceWithoutConstructor();
         $properties = self::getClassProperties($className);
 
         foreach ($payload as $key => $value) {
diff --git a/src/Members/Members.php b/src/Members/Members.php
index 050ea00..f622914 100644
--- a/src/Members/Members.php
+++ b/src/Members/Members.php
@@ -63,15 +63,65 @@ class MembersCreateRequest
      */
     public ?array $attributes = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param string $email
+     * @param string[] $roles
+     * @param bool|null $isManagedUser
+     * @param string|null $password
+     * @param string|null $nickname
+     * @param array<string, mixed>|null $metadata
+     * @param array<string, mixed>|null $attributes
+     */
+    public function __construct(
+        string $email,
+        array $roles,
+        ?bool $isManagedUser = null,
+        ?string $password = null,
+        ?string $nickname = null,
+        ?array $metadata = null,
+        ?array $attributes = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'email' => $email,
+            'roles' => $roles,
+            'is_managed_user' => $isManagedUser,
+            'password' => $password,
+            'nickname' => $nickname,
+            'metadata' => $metadata,
+            'attributes' => $attributes,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
+        self::assertRequiredFields($data, [
+            'email' => 'email',
+            'roles' => 'roles',
+        ]);
+
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
+    }
+
+    /**
+     * @param array<string, mixed> $data
+     * @param array<string, string> $requiredFields
+     */
+    private static function assertRequiredFields(array $data, array $requiredFields): void
+    {
+        foreach ($requiredFields as $serializedName => $propertyName) {
+            if (!array_key_exists($serializedName, $data) && !array_key_exists($propertyName, $data)) {
+                throw new \InvalidArgumentException(sprintf('Missing required field "%s".', $serializedName));
+            }
         }
     }
 
@@ -106,16 +156,39 @@ class MembersUpdateRequest
      */
     public ?MembersUpdateRequestUser $user = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param string[]|null $roles
+     * @param array<string, mixed>|null $metadata
+     * @param array<string, mixed>|null $attributes
+     * @param MembersUpdateRequestUser|null $user
+     */
+    public function __construct(
+        ?array $roles = null,
+        ?array $metadata = null,
+        ?array $attributes = null,
+        ?MembersUpdateRequestUser $user = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'roles' => $roles,
+            'metadata' => $metadata,
+            'attributes' => $attributes,
+            'user' => $user,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
-        }
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
     }
 
 }
@@ -267,7 +340,11 @@ public function create(string $merchantCode, MembersCreateRequest|array $body, ?
     {
         $path = sprintf('/v0.1/merchants/%s/members', rawurlencode((string) $merchantCode));
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = MembersCreateRequest::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
@@ -417,7 +494,11 @@ public function update(string $merchantCode, string $memberId, MembersUpdateRequ
     {
         $path = sprintf('/v0.1/merchants/%s/members/%s', rawurlencode((string) $merchantCode), rawurlencode((string) $memberId));
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = MembersUpdateRequest::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
diff --git a/src/Readers/Readers.php b/src/Readers/Readers.php
index f6d49c6..9d03c56 100644
--- a/src/Readers/Readers.php
+++ b/src/Readers/Readers.php
@@ -35,15 +35,53 @@ class ReadersCreateRequest
      */
     public ?array $metadata = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param string $pairingCode
+     * @param string $name
+     * @param array<string, mixed>|null $metadata
+     */
+    public function __construct(
+        string $pairingCode,
+        string $name,
+        ?array $metadata = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'pairing_code' => $pairingCode,
+            'name' => $name,
+            'metadata' => $metadata,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
+        self::assertRequiredFields($data, [
+            'pairing_code' => 'pairingCode',
+            'name' => 'name',
+        ]);
+
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
+    }
+
+    /**
+     * @param array<string, mixed> $data
+     * @param array<string, string> $requiredFields
+     */
+    private static function assertRequiredFields(array $data, array $requiredFields): void
+    {
+        foreach ($requiredFields as $serializedName => $propertyName) {
+            if (!array_key_exists($serializedName, $data) && !array_key_exists($propertyName, $data)) {
+                throw new \InvalidArgumentException(sprintf('Missing required field "%s".', $serializedName));
+            }
         }
     }
 
@@ -56,6 +94,15 @@ public function __construct(array $data = [])
  */
 class ReadersTerminateCheckoutRequest
 {
+    /**
+     * Create request DTO from an associative array.
+     *
+     * @param array<string, mixed> $data
+     */
+    public static function fromArray(array $data): self
+    {
+        return new self();
+    }
 }
 
 class ReadersUpdateRequest
@@ -74,16 +121,33 @@ class ReadersUpdateRequest
      */
     public ?array $metadata = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param string|null $name
+     * @param array<string, mixed>|null $metadata
+     */
+    public function __construct(
+        ?string $name = null,
+        ?array $metadata = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'name' => $name,
+            'metadata' => $metadata,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
-        }
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
     }
 
 }
@@ -150,7 +214,11 @@ public function create(string $merchantCode, ReadersCreateRequest|array $body, ?
     {
         $path = sprintf('/v0.1/merchants/%s/readers', rawurlencode((string) $merchantCode));
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = ReadersCreateRequest::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
@@ -184,7 +252,11 @@ public function createCheckout(string $merchantCode, string $readerId, \SumUp\Ty
     {
         $path = sprintf('/v0.1/merchants/%s/readers/%s/checkout', rawurlencode((string) $merchantCode), rawurlencode((string) $readerId));
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = \SumUp\Types\CreateReaderCheckoutRequest::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
@@ -335,7 +407,11 @@ public function terminateCheckout(string $merchantCode, string $readerId, Reader
         $path = sprintf('/v0.1/merchants/%s/readers/%s/terminate', rawurlencode((string) $merchantCode), rawurlencode((string) $readerId));
         $payload = [];
         if ($body !== null) {
-            $payload = RequestEncoder::encode($body);
+            $requestBody = $body;
+            if (is_array($requestBody)) {
+                $requestBody = ReadersTerminateCheckoutRequest::fromArray($requestBody);
+            }
+            $payload = RequestEncoder::encode($requestBody);
         }
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
@@ -371,7 +447,11 @@ public function update(string $merchantCode, string $id, ReadersUpdateRequest|ar
     {
         $path = sprintf('/v0.1/merchants/%s/readers/%s', rawurlencode((string) $merchantCode), rawurlencode((string) $id));
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = ReadersUpdateRequest::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
diff --git a/src/Roles/Roles.php b/src/Roles/Roles.php
index 7bd03f4..7487424 100644
--- a/src/Roles/Roles.php
+++ b/src/Roles/Roles.php
@@ -42,15 +42,56 @@ class RolesCreateRequest
      */
     public ?string $description = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param string $name
+     * @param string[] $permissions
+     * @param array<string, mixed>|null $metadata
+     * @param string|null $description
+     */
+    public function __construct(
+        string $name,
+        array $permissions,
+        ?array $metadata = null,
+        ?string $description = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'name' => $name,
+            'permissions' => $permissions,
+            'metadata' => $metadata,
+            'description' => $description,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
+    {
+        self::assertRequiredFields($data, [
+            'name' => 'name',
+            'permissions' => 'permissions',
+        ]);
+
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
+    }
+
+    /**
+     * @param array<string, mixed> $data
+     * @param array<string, string> $requiredFields
+     */
+    private static function assertRequiredFields(array $data, array $requiredFields): void
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
+        foreach ($requiredFields as $serializedName => $propertyName) {
+            if (!array_key_exists($serializedName, $data) && !array_key_exists($propertyName, $data)) {
+                throw new \InvalidArgumentException(sprintf('Missing required field "%s".', $serializedName));
+            }
         }
     }
 
@@ -79,16 +120,36 @@ class RolesUpdateRequest
      */
     public ?string $description = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param string|null $name
+     * @param string[]|null $permissions
+     * @param string|null $description
+     */
+    public function __construct(
+        ?string $name = null,
+        ?array $permissions = null,
+        ?string $description = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'name' => $name,
+            'permissions' => $permissions,
+            'description' => $description,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
-        }
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
     }
 
 }
@@ -155,7 +216,11 @@ public function create(string $merchantCode, RolesCreateRequest|array $body, ?Re
     {
         $path = sprintf('/v0.1/merchants/%s/roles', rawurlencode((string) $merchantCode));
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = RolesCreateRequest::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
@@ -274,7 +339,11 @@ public function update(string $merchantCode, string $roleId, RolesUpdateRequest|
     {
         $path = sprintf('/v0.1/merchants/%s/roles/%s', rawurlencode((string) $merchantCode), rawurlencode((string) $roleId));
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = RolesUpdateRequest::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
diff --git a/src/Subaccounts/Subaccounts.php b/src/Subaccounts/Subaccounts.php
index 4cfa8c4..2d6ffca 100644
--- a/src/Subaccounts/Subaccounts.php
+++ b/src/Subaccounts/Subaccounts.php
@@ -38,15 +38,56 @@ class SubaccountsCreateSubAccountRequest
      */
     public ?SubaccountsCreateSubAccountRequestPermissions $permissions = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param string $username
+     * @param string $password
+     * @param string|null $nickname
+     * @param SubaccountsCreateSubAccountRequestPermissions|null $permissions
+     */
+    public function __construct(
+        string $username,
+        string $password,
+        ?string $nickname = null,
+        ?SubaccountsCreateSubAccountRequestPermissions $permissions = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'username' => $username,
+            'password' => $password,
+            'nickname' => $nickname,
+            'permissions' => $permissions,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
+        self::assertRequiredFields($data, [
+            'username' => 'username',
+            'password' => 'password',
+        ]);
+
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
+    }
+
+    /**
+     * @param array<string, mixed> $data
+     * @param array<string, string> $requiredFields
+     */
+    private static function assertRequiredFields(array $data, array $requiredFields): void
+    {
+        foreach ($requiredFields as $serializedName => $propertyName) {
+            if (!array_key_exists($serializedName, $data) && !array_key_exists($propertyName, $data)) {
+                throw new \InvalidArgumentException(sprintf('Missing required field "%s".', $serializedName));
+            }
         }
     }
 
@@ -84,16 +125,42 @@ class SubaccountsUpdateSubAccountRequest
      */
     public ?SubaccountsUpdateSubAccountRequestPermissions $permissions = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param string|null $password
+     * @param string|null $username
+     * @param bool|null $disabled
+     * @param string|null $nickname
+     * @param SubaccountsUpdateSubAccountRequestPermissions|null $permissions
+     */
+    public function __construct(
+        ?string $password = null,
+        ?string $username = null,
+        ?bool $disabled = null,
+        ?string $nickname = null,
+        ?SubaccountsUpdateSubAccountRequestPermissions $permissions = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'password' => $password,
+            'username' => $username,
+            'disabled' => $disabled,
+            'nickname' => $nickname,
+            'permissions' => $permissions,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
-        }
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
     }
 
 }
@@ -261,7 +328,11 @@ public function createSubAccount(SubaccountsCreateSubAccountRequest|array $body,
     {
         $path = '/v0.1/me/accounts';
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = SubaccountsCreateSubAccountRequest::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
@@ -338,7 +409,11 @@ public function updateSubAccount(string $operatorId, SubaccountsUpdateSubAccount
     {
         $path = sprintf('/v0.1/me/accounts/%s', rawurlencode((string) $operatorId));
         $payload = [];
-        $payload = RequestEncoder::encode($body);
+        $requestBody = $body;
+        if (is_array($requestBody)) {
+            $requestBody = SubaccountsUpdateSubAccountRequest::fromArray($requestBody);
+        }
+        $payload = RequestEncoder::encode($requestBody);
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
         $headers['Authorization'] = 'Bearer ' . $this->accessToken;
diff --git a/src/Transactions/Transactions.php b/src/Transactions/Transactions.php
index 82753d9..9fccc14 100644
--- a/src/Transactions/Transactions.php
+++ b/src/Transactions/Transactions.php
@@ -24,16 +24,30 @@ class TransactionsRefundRequest
      */
     public ?float $amount = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param float|null $amount
+     */
+    public function __construct(
+        ?float $amount = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'amount' => $amount,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
-        }
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
     }
 
 }
@@ -660,7 +674,11 @@ public function refund(string $txnId, TransactionsRefundRequest|array|null $body
         $path = sprintf('/v0.1/me/refund/%s', rawurlencode((string) $txnId));
         $payload = [];
         if ($body !== null) {
-            $payload = RequestEncoder::encode($body);
+            $requestBody = $body;
+            if (is_array($requestBody)) {
+                $requestBody = TransactionsRefundRequest::fromArray($requestBody);
+            }
+            $payload = RequestEncoder::encode($requestBody);
         }
         $headers = ['Content-Type' => 'application/json', 'User-Agent' => SdkInfo::getUserAgent()];
         $headers = array_merge($headers, SdkInfo::getRuntimeHeaders());
diff --git a/src/Types/CheckoutCreateRequest.php b/src/Types/CheckoutCreateRequest.php
index 4e56259..fb7abab 100644
--- a/src/Types/CheckoutCreateRequest.php
+++ b/src/Types/CheckoutCreateRequest.php
@@ -79,15 +79,76 @@ class CheckoutCreateRequest
      */
     public ?string $redirectUrl = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param string $checkoutReference
+     * @param float $amount
+     * @param CheckoutCreateRequestCurrency|string $currency
+     * @param string $merchantCode
+     * @param string|null $description
+     * @param string|null $returnUrl
+     * @param string|null $customerId
+     * @param CheckoutCreateRequestPurpose|string|null $purpose
+     * @param string|null $validUntil
+     * @param string|null $redirectUrl
+     */
+    public function __construct(
+        string $checkoutReference,
+        float $amount,
+        CheckoutCreateRequestCurrency|string $currency,
+        string $merchantCode,
+        ?string $description = null,
+        ?string $returnUrl = null,
+        ?string $customerId = null,
+        CheckoutCreateRequestPurpose|string|null $purpose = null,
+        ?string $validUntil = null,
+        ?string $redirectUrl = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'checkout_reference' => $checkoutReference,
+            'amount' => $amount,
+            'currency' => $currency,
+            'merchant_code' => $merchantCode,
+            'description' => $description,
+            'return_url' => $returnUrl,
+            'customer_id' => $customerId,
+            'purpose' => $purpose,
+            'valid_until' => $validUntil,
+            'redirect_url' => $redirectUrl,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
+    {
+        self::assertRequiredFields($data, [
+            'checkout_reference' => 'checkoutReference',
+            'amount' => 'amount',
+            'currency' => 'currency',
+            'merchant_code' => 'merchantCode',
+        ]);
+
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
+    }
+
+    /**
+     * @param array<string, mixed> $data
+     * @param array<string, string> $requiredFields
+     */
+    private static function assertRequiredFields(array $data, array $requiredFields): void
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
+        foreach ($requiredFields as $serializedName => $propertyName) {
+            if (!array_key_exists($serializedName, $data) && !array_key_exists($propertyName, $data)) {
+                throw new \InvalidArgumentException(sprintf('Missing required field "%s".', $serializedName));
+            }
         }
     }
 
diff --git a/src/Types/CreateReaderCheckoutRequest.php b/src/Types/CreateReaderCheckoutRequest.php
index 34df644..cededd1 100644
--- a/src/Types/CreateReaderCheckoutRequest.php
+++ b/src/Types/CreateReaderCheckoutRequest.php
@@ -87,15 +87,70 @@ class CreateReaderCheckoutRequest
      */
     public CreateReaderCheckoutRequestTotalAmount $totalAmount;
 
+    /**
+     * Create request DTO.
+     *
+     * @param CreateReaderCheckoutRequestTotalAmount $totalAmount
+     * @param CreateReaderCheckoutRequestAade|null $aade
+     * @param CreateReaderCheckoutRequestAffiliate|null $affiliate
+     * @param CreateReaderCheckoutRequestCardType|string|null $cardType
+     * @param string|null $description
+     * @param int|null $installments
+     * @param string|null $returnUrl
+     * @param float[]|null $tipRates
+     * @param int|null $tipTimeout
+     */
+    public function __construct(
+        CreateReaderCheckoutRequestTotalAmount $totalAmount,
+        ?CreateReaderCheckoutRequestAade $aade = null,
+        ?CreateReaderCheckoutRequestAffiliate $affiliate = null,
+        CreateReaderCheckoutRequestCardType|string|null $cardType = null,
+        ?string $description = null,
+        ?int $installments = null,
+        ?string $returnUrl = null,
+        ?array $tipRates = null,
+        ?int $tipTimeout = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'total_amount' => $totalAmount,
+            'aade' => $aade,
+            'affiliate' => $affiliate,
+            'card_type' => $cardType,
+            'description' => $description,
+            'installments' => $installments,
+            'return_url' => $returnUrl,
+            'tip_rates' => $tipRates,
+            'tip_timeout' => $tipTimeout,
+        ], self::class, $this);
+    }
+
     /**
      * Create request DTO from an associative array.
      *
      * @param array<string, mixed> $data
      */
-    public function __construct(array $data = [])
+    public static function fromArray(array $data): self
+    {
+        self::assertRequiredFields($data, [
+            'total_amount' => 'totalAmount',
+        ]);
+
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
+    }
+
+    /**
+     * @param array<string, mixed> $data
+     * @param array<string, string> $requiredFields
+     */
+    private static function assertRequiredFields(array $data, array $requiredFields): void
     {
-        if ($data !== []) {
-            \SumUp\Hydrator::hydrate($data, self::class, $this);
+        foreach ($requiredFields as $serializedName => $propertyName) {
+            if (!array_key_exists($serializedName, $data) && !array_key_exists($propertyName, $data)) {
+                throw new \InvalidArgumentException(sprintf('Missing required field "%s".', $serializedName));
+            }
         }
     }
 
diff --git a/src/Types/Customer.php b/src/Types/Customer.php
index c5d2ec1..9c191fc 100644
--- a/src/Types/Customer.php
+++ b/src/Types/Customer.php
@@ -23,4 +23,50 @@ class Customer
      */
     public ?PersonalDetails $personalDetails = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param string $customerId
+     * @param PersonalDetails|null $personalDetails
+     */
+    public function __construct(
+        string $customerId,
+        ?PersonalDetails $personalDetails = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'customer_id' => $customerId,
+            'personal_details' => $personalDetails,
+        ], self::class, $this);
+    }
+
+    /**
+     * Create request DTO from an associative array.
+     *
+     * @param array<string, mixed> $data
+     */
+    public static function fromArray(array $data): self
+    {
+        self::assertRequiredFields($data, [
+            'customer_id' => 'customerId',
+        ]);
+
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
+    }
+
+    /**
+     * @param array<string, mixed> $data
+     * @param array<string, string> $requiredFields
+     */
+    private static function assertRequiredFields(array $data, array $requiredFields): void
+    {
+        foreach ($requiredFields as $serializedName => $propertyName) {
+            if (!array_key_exists($serializedName, $data) && !array_key_exists($propertyName, $data)) {
+                throw new \InvalidArgumentException(sprintf('Missing required field "%s".', $serializedName));
+            }
+        }
+    }
+
 }
diff --git a/src/Types/ProcessCheckout.php b/src/Types/ProcessCheckout.php
index 918b4c6..06384fc 100644
--- a/src/Types/ProcessCheckout.php
+++ b/src/Types/ProcessCheckout.php
@@ -72,4 +72,71 @@ class ProcessCheckout
      */
     public ?PersonalDetails $personalDetails = null;
 
+    /**
+     * Create request DTO.
+     *
+     * @param ProcessCheckoutPaymentType|string $paymentType
+     * @param int|null $installments
+     * @param MandatePayload|null $mandate
+     * @param Card|null $card
+     * @param array<string, mixed>|null $googlePay
+     * @param array<string, mixed>|null $applePay
+     * @param string|null $token
+     * @param string|null $customerId
+     * @param PersonalDetails|null $personalDetails
+     */
+    public function __construct(
+        ProcessCheckoutPaymentType|string $paymentType,
+        ?int $installments = null,
+        ?MandatePayload $mandate = null,
+        ?Card $card = null,
+        ?array $googlePay = null,
+        ?array $applePay = null,
+        ?string $token = null,
+        ?string $customerId = null,
+        ?PersonalDetails $personalDetails = null
+    ) {
+        \SumUp\Hydrator::hydrate([
+            'payment_type' => $paymentType,
+            'installments' => $installments,
+            'mandate' => $mandate,
+            'card' => $card,
+            'google_pay' => $googlePay,
+            'apple_pay' => $applePay,
+            'token' => $token,
+            'customer_id' => $customerId,
+            'personal_details' => $personalDetails,
+        ], self::class, $this);
+    }
+
+    /**
+     * Create request DTO from an associative array.
+     *
+     * @param array<string, mixed> $data
+     */
+    public static function fromArray(array $data): self
+    {
+        self::assertRequiredFields($data, [
+            'payment_type' => 'paymentType',
+        ]);
+
+        $request = (new \ReflectionClass(self::class))->newInstanceWithoutConstructor();
+        \SumUp\Hydrator::hydrate($data, self::class, $request);
+
+        return $request;
+    }
+
+    /**
+     * @param array<string, mixed> $data
+     * @param array<string, string> $requiredFields
+     */
+    private static function assertRequiredFields(array $data, array $requiredFields): void
+    {
+        foreach ($requiredFields as $serializedName => $propertyName) {
+            if (!array_key_exists($serializedName, $data) && !array_key_exists($propertyName, $data)) {
+                throw new \InvalidArgumentException(sprintf('Missing required field "%s".', $serializedName));
+            }
+        }
+    }
+
 }
diff --git a/tests/RequestEncoderTest.php b/tests/RequestEncoderTest.php
index c70be93..c056e4c 100644
--- a/tests/RequestEncoderTest.php
+++ b/tests/RequestEncoderTest.php
@@ -18,11 +18,12 @@ public function testEncodeLeavesArrayPayloadUntouched()
 
     public function testEncodeConvertsDtoToSnakeCaseAndBackedEnumValues()
     {
-        $request = new CheckoutCreateRequest();
-        $request->checkoutReference = 'order-123';
-        $request->amount = 10.0;
-        $request->currency = CheckoutCreateRequestCurrency::EUR;
-        $request->merchantCode = 'MC123';
+        $request = new CheckoutCreateRequest(
+            checkoutReference: 'order-123',
+            amount: 10.0,
+            currency: CheckoutCreateRequestCurrency::EUR,
+            merchantCode: 'MC123',
+        );
 
         $encoded = RequestEncoder::encode($request);
 
diff --git a/tests/TypesRequestConstructorTest.php b/tests/TypesRequestConstructorTest.php
index d884fbc..a109271 100644
--- a/tests/TypesRequestConstructorTest.php
+++ b/tests/TypesRequestConstructorTest.php
@@ -9,17 +9,19 @@
 use SumUp\Types\CreateReaderCheckoutRequestAade;
 use SumUp\Types\CreateReaderCheckoutRequestAffiliate;
 use SumUp\Types\CreateReaderCheckoutRequestTotalAmount;
+use SumUp\Types\ProcessCheckout;
+use SumUp\Types\ProcessCheckoutPaymentType;
 
 class TypesRequestConstructorTest extends TestCase
 {
-    public function testCheckoutCreateRequestSupportsArrayInputWithEnumCoercion(): void
+    public function testCheckoutCreateRequestSupportsNamedArgumentsWithEnumCoercion(): void
     {
-        $request = new CheckoutCreateRequest([
-            'checkout_reference' => 'ref-123',
-            'amount' => 10,
-            'currency' => 'EUR',
-            'merchant_code' => 'MERCHANT-1',
-        ]);
+        $request = new CheckoutCreateRequest(
+            checkoutReference: 'ref-123',
+            amount: 10,
+            currency: 'EUR',
+            merchantCode: 'MERCHANT-1',
+        );
 
         $this->assertSame('ref-123', $request->checkoutReference);
         $this->assertSame(10.0, $request->amount);
@@ -27,9 +29,9 @@ public function testCheckoutCreateRequestSupportsArrayInputWithEnumCoercion(): v
         $this->assertSame('MERCHANT-1', $request->merchantCode);
     }
 
-    public function testCheckoutCreateRequestIgnoresUnknownProperty(): void
+    public function testCheckoutCreateRequestFromArrayIgnoresUnknownProperty(): void
     {
-        $request = new CheckoutCreateRequest([
+        $request = CheckoutCreateRequest::fromArray([
             'checkout_reference' => 'ref-123',
             'amount' => 10.0,
             'currency' => CheckoutCreateRequestCurrency::EUR,
@@ -40,18 +42,19 @@ public function testCheckoutCreateRequestIgnoresUnknownProperty(): void
         $this->assertSame('ref-123', $request->checkoutReference);
     }
 
-    public function testCheckoutCreateRequestAllowsPartialInput(): void
+    public function testCheckoutCreateRequestFromArrayRequiresRequiredFields(): void
     {
-        $request = new CheckoutCreateRequest([
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Missing required field "amount".');
+
+        CheckoutCreateRequest::fromArray([
             'checkout_reference' => 'ref-123',
         ]);
-
-        $this->assertSame('ref-123', $request->checkoutReference);
     }
 
     public function testCreateReaderCheckoutRequestHydratesInlineObjectProperties(): void
     {
-        $request = new CreateReaderCheckoutRequest([
+        $request = CreateReaderCheckoutRequest::fromArray([
             'aade' => [
                 'provider_id' => 'provider-123',
                 'signature' => 'base64-signature',
@@ -85,4 +88,13 @@ public function testCreateReaderCheckoutRequestHydratesInlineObjectProperties():
         $this->assertSame(2, $request->totalAmount->minorUnit);
         $this->assertSame(100, $request->totalAmount->value);
     }
+
+    public function testRequestBodyDtoWithoutRequestSuffixSupportsNamedArgumentsAndFromArray(): void
+    {
+        $namedRequest = new ProcessCheckout(paymentType: 'card');
+        $arrayRequest = ProcessCheckout::fromArray(['payment_type' => 'card']);
+
+        $this->assertSame(ProcessCheckoutPaymentType::CARD, $namedRequest->paymentType);
+        $this->assertSame(ProcessCheckoutPaymentType::CARD, $arrayRequest->paymentType);
+    }
 }