diff --git a/src/typechat.ts b/src/typechat.ts
index 3ab774f6..47763d26 100644
--- a/src/typechat.ts
+++ b/src/typechat.ts
@@ -2,117 +2,100 @@ import { Result, error } from "./result";
 import { TypeChatLanguageModel } from "./model";
 import { TypeChatJsonValidator, createJsonValidator } from "./validate";
 
-/**
- * Represents an object that can translate natural language requests in JSON objects of the given type.
- */
-export interface TypeChatJsonTranslator<T extends object> {
-    /**
-     * The associated `TypeChatLanguageModel`.
-     */
-    model: TypeChatLanguageModel;
-    /**
-     * The associated `TypeChatJsonValidator<T>`.
-     */
-    validator: TypeChatJsonValidator<T>;
-    /**
-     * A boolean indicating whether to attempt repairing JSON objects that fail to validate. The default is `true`,
-     * but an application can set the property to `false` to disable repair attempts.
-     */
-    attemptRepair:  boolean;
-    /**
-     * A boolean indicating whether to delete properties with null values from parsed JSON objects. Some language
-     * models (e.g. gpt-3.5-turbo) have a tendency to assign null values to optional properties instead of omitting
-     * them. The default for this property is `false`, but an application can set the property to `true` for schemas
-     * that don't permit null values.
-     */
-    stripNulls:  boolean;
-    /**
-     * Creates an AI language model prompt from the given request. This function is called by `completeAndValidate`
-     * to obtain the prompt. An application can assign a new function to provide a different prompt.
-     * @param request The natural language request.
-     * @returns A prompt that combines the request with the schema and type name of the underlying validator.
-     */
-    createRequestPrompt(request: string): string;
-    /**
-     * Creates a repair prompt to append to an original prompt/response in order to repair a JSON object that
-     * failed to validate. This function is called by `completeAndValidate` when `attemptRepair` is true and the
-     * JSON object produced by the original prompt failed to validate. An application can assign a new function
-     * to provide a different repair prompt.
-     * @param validationError The error message returned by the validator.
-     * @returns A repair prompt constructed from the error message.
-     */
-    createRepairPrompt(validationError: string): string;
-    /**
-     * Translates a natural language request into an object of type `T`. If the JSON object returned by
-     * the language model fails to validate and the `attemptRepair` property is `true`, a second
-     * attempt to translate the request will be made. The prompt for the second attempt will include the
-     * diagnostics produced for the first attempt. This often helps produce a valid instance.
-     * @param request The natural language request.
-     * @returns A promise for the resulting object.
-     */
-    translate(request: string): Promise<Result<T>>;
+interface TypeChatJsonTranslator<T extends object> {
+  model: TypeChatLanguageModel;
+  validator: TypeChatJsonValidator<T>;
+  attemptRepair: boolean;
+  stripNulls: boolean;
+  createRequestPrompt: (naturalLanguageRequest: string) => string;
+  createRepairPrompt: (validationError: string) => string;
+  translate: (naturalLanguageRequest: string) => Promise<Result<T>>;
 }
 
-/**
- * Creates an object that can translate natural language requests into JSON objects of the given type.
- * The specified type argument `T` must be the same type as `typeName` in the given `schema`. The function
- * creates a `TypeChatJsonValidator<T>` and stores it in the `validator` property of the returned instance.
- * @param model The language model to use for translating requests into JSON.
- * @param schema A string containing the TypeScript source code for the JSON schema.
- * @param typeName The name of the JSON target type in the schema.
- * @returns A `TypeChatJsonTranslator<T>` instance.
- */
-export function createJsonTranslator<T extends object>(model: TypeChatLanguageModel, schema: string, typeName: string): TypeChatJsonTranslator<T> {
-    const validator = createJsonValidator<T>(schema, typeName);
-    const typeChat: TypeChatJsonTranslator<T> = {
-        model,
-        validator,
-        attemptRepair: true,
-        stripNulls: false,
-        createRequestPrompt,
-        createRepairPrompt,
-        translate
-    };
-    return typeChat;
-
-    function createRequestPrompt(request: string) {
-        return `You are a service that translates user requests into JSON objects of type "${validator.typeName}" according to the following TypeScript definitions:\n` +
-            `\`\`\`\n${validator.schema}\`\`\`\n` +
-            `The following is a user request:\n` +
-            `"""\n${request}\n"""\n` +
-            `The following is the user request translated into a JSON object with 2 spaces of indentation and no properties with the value undefined:\n`;
-    }
-
-    function createRepairPrompt(validationError: string) {
-        return `The JSON object is invalid for the following reason:\n` +
-            `"""\n${validationError}\n"""\n` +
-            `The following is a revised JSON object:\n`;
-    }
-
-    async function translate(request: string) {
-        let prompt = typeChat.createRequestPrompt(request);
-        let attemptRepair = typeChat.attemptRepair;
-        while (true) {
-            const response = await model.complete(prompt);
-            if (!response.success) {
-                return response;
-            }
-            const responseText = response.data;
-            const startIndex = responseText.indexOf("{");
-            const endIndex = responseText.lastIndexOf("}");
-            if (!(startIndex >= 0 && endIndex > startIndex)) {
-                return error(`Response is not JSON:\n${responseText}`);
-            }
-            const jsonText = responseText.slice(startIndex, endIndex + 1);
-            const validation = validator.validate(jsonText);
-            if (validation.success) {
-                return validation;
-            }
-            if (!attemptRepair) {
-                return error(`JSON validation failed: ${validation.message}\n${jsonText}`);
-            }
-            prompt += `${responseText}\n${typeChat.createRepairPrompt(validation.message)}`;
-            attemptRepair = false;
+function createJsonTranslator<T extends object>(
+  model: TypeChatLanguageModel,
+  schema: string,
+  typeName: string
+): TypeChatJsonTranslator<T> {
+  const validator = createJsonValidator<T>(schema, typeName);
+
+  const translator: TypeChatJsonTranslator<T> = {
+    model,
+    validator,
+    attemptRepair: true,
+    stripNulls: false,
+
+    createRequestPrompt(naturalLanguageRequest) {
+      return `
+          You are a service that translates user requests into JSON objects of type "${this.validator.typeName}" according to the following TypeScript definitions:
+          
+          \`\`\`
+          ${this.validator.schema}
+          \`\`\`
+          
+          The following is a user request:
+          
+          """
+          ${naturalLanguageRequest}
+          """
+          
+          The following is the user request translated into a JSON object with 2 spaces of indentation and no properties with the value undefined:
+        `;
+    },
+
+    createRepairPrompt(validationError) {
+      return `
+          The JSON object is invalid for the following reason:
+          
+          """
+          ${validationError}
+          """
+        
+          The following is a revised JSON object:
+        `;
+    },
+
+    async translate(naturalLanguageRequest) {
+      let prompt = this.createRequestPrompt(naturalLanguageRequest);
+      let attemptRepair = this.attemptRepair;
+
+      while (true) {
+        const response = await this.model.complete(prompt);
+
+        if (!response.success) {
+          return response;
+        }
+
+        const aiResponseText = response.data;
+        const startIndex = aiResponseText.indexOf("{");
+        const endIndex = aiResponseText.lastIndexOf("}");
+
+        if (startIndex == -1 || endIndex == -1 || startIndex >= endIndex) {
+          // invalid JSON, return error
         }
-    }
+
+        const parsedJsonText = aiResponseText.slice(startIndex, endIndex + 1);
+
+        const validation = this.validator.validate(parsedJsonText);
+
+        if (validation.success) {
+          return validation;
+        }
+
+        if (!attemptRepair) {
+          return error(
+            `JSON validation failed: ${validation.message}\n${parsedJsonText}`
+          );
+        }
+
+        prompt += `${aiResponseText}\n${this.createRepairPrompt(
+          validation.message
+        )}`;
+
+        attemptRepair = false;
+      }
+    },
+  };
+
+  return translator;
 }