diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5da0f080..f18272a2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # CHANGELOG
 
+## v2.3.1
+
+### Date: 03-Nov-2025
+
+- Github issue fix
+- Improved error messages
+
 ## v2.3.0
 
 ### Date: 29-Sep-2025
diff --git a/pom.xml b/pom.xml
index 46dce80c..7d86dffe 100644
--- a/pom.xml
+++ b/pom.xml
@@ -5,7 +5,7 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.contentstack.sdk</groupId>
     <artifactId>java</artifactId>
-    <version>2.3.0</version>
+    <version>2.3.1</version>
     <packaging>jar</packaging>
     <name>contentstack-java</name>
     <description>Java SDK for Contentstack Content Delivery API</description>
diff --git a/src/main/java/com/contentstack/sdk/AssetLibrary.java b/src/main/java/com/contentstack/sdk/AssetLibrary.java
index dd168723..e005955f 100644
--- a/src/main/java/com/contentstack/sdk/AssetLibrary.java
+++ b/src/main/java/com/contentstack/sdk/AssetLibrary.java
@@ -179,7 +179,11 @@ public AssetLibrary addParam(@NotNull String paramKey, @NotNull Object paramValu
         if (isValidKey(paramKey) && isValidValue(paramValue)) {
             urlQueries.put(paramKey, paramValue);
         } else {
-            logger.warning("Invalid key or value");
+            if (!isValidKey(paramKey)) {
+                logger.warning(ErrorMessages.INVALID_PARAMETER_KEY);
+            } else {
+                logger.warning(ErrorMessages.INVALID_PARAMETER_VALUE);
+            }
         }
         return this;
     }
@@ -310,9 +314,10 @@ public void getResultObject(List<Object> objects, JSONObject jsonObject, boolean
 
         List<Asset> assets = new ArrayList<>();
 
-        // if (objects == null || objects.isEmpty()) {
-        //     System.out.println("Objects list is null or empty");
-        // }
+        if (objects == null || objects.isEmpty()) {
+            logger.warning(ErrorMessages.MISSING_ASSETS_LIST);
+            return;
+        }
 
         if (objects != null && !objects.isEmpty()) {
             for (Object object : objects) {
@@ -328,9 +333,9 @@ public void getResultObject(List<Object> objects, JSONObject jsonObject, boolean
                 assets.add(asset);
             }
         } 
-        // else {
-        // System.out.println("Object is not an instance of AssetModel");
-        // }
+        else {
+            logger.warning(ErrorMessages.INVALID_OBJECT_TYPE_ASSET_MODEL);
+        }
 
         if (callback != null) {
             callback.onRequestFinish(ResponseType.NETWORK, assets);
@@ -351,7 +356,11 @@ public AssetLibrary where(String key, String value) {
             queryParams.put(key,value);
             urlQueries.put("query", queryParams);
         } else {
-            throw new IllegalArgumentException("Invalid key or value");
+            if (!isValidKey(key)) {
+                throw new IllegalArgumentException(ErrorMessages.INVALID_PARAMETER_KEY);
+            } else {
+                throw new IllegalArgumentException(ErrorMessages.INVALID_PARAMETER_VALUE);
+            }
         }
         return this;
     }
diff --git a/src/main/java/com/contentstack/sdk/AssetsModel.java b/src/main/java/com/contentstack/sdk/AssetsModel.java
index f5879952..97b653b4 100644
--- a/src/main/java/com/contentstack/sdk/AssetsModel.java
+++ b/src/main/java/com/contentstack/sdk/AssetsModel.java
@@ -31,7 +31,7 @@ public AssetsModel(JSONObject response) {
             List<?> assetsList = (List<?>) rawAssets;
             listResponse = new JSONArray(assetsList); // Convert to JSONArray
         } else if (rawAssets != null) {
-            throw new IllegalArgumentException("Invalid type for 'assets' key: " + rawAssets.getClass().getName());
+            throw new IllegalArgumentException(ErrorMessages.INVALID_ASSETS_TYPE);
         }
         if (listResponse != null) {
             listResponse.forEach(model -> {
diff --git a/src/main/java/com/contentstack/sdk/CSBackgroundTask.java b/src/main/java/com/contentstack/sdk/CSBackgroundTask.java
index aaebb39f..e1fe2eb7 100644
--- a/src/main/java/com/contentstack/sdk/CSBackgroundTask.java
+++ b/src/main/java/com/contentstack/sdk/CSBackgroundTask.java
@@ -93,7 +93,7 @@ protected void checkHeader(@NotNull Map<String, Object> headers) {
         final Logger logger = Logger.getLogger("CSBackgroundTask");
         if (headers.size() == 0) {
             try {
-                throw new IllegalAccessException("CSBackgroundTask Header Exception");
+                throw new IllegalAccessException(ErrorMessages.MISSING_REQUEST_HEADERS);
             } catch (IllegalAccessException e) {
                 logger.log(Level.SEVERE, e.getLocalizedMessage(), e);
             }
diff --git a/src/main/java/com/contentstack/sdk/CSHttpConnection.java b/src/main/java/com/contentstack/sdk/CSHttpConnection.java
index 875f58d2..9635dbf5 100644
--- a/src/main/java/com/contentstack/sdk/CSHttpConnection.java
+++ b/src/main/java/com/contentstack/sdk/CSHttpConnection.java
@@ -158,7 +158,7 @@ private String getParams(HashMap<String, Object> params) {
                     urlParams += urlParams.equals("?") ? key + "=" + value : "&" + key + "=" + value;
                 }
             } catch (Exception e1) {
-                logger.log(Level.SEVERE, e1.getLocalizedMessage(), e1);
+                logger.log(Level.SEVERE, ErrorMessages.URL_PARAMETER_ENCODING_FAILED, e1);
             }
         }
         return urlParams;
@@ -187,7 +187,7 @@ public void send() {
         try {
             getService(url);
         } catch (IOException | JSONException e) {
-            logger.log(Level.SEVERE, e.getLocalizedMessage(), e);
+            logger.log(Level.SEVERE, ErrorMessages.URL_PARAMETER_ENCODING_FAILED, e);
         }
     }
 
@@ -238,7 +238,7 @@ private void getService(String requestUrl) throws IOException {
                     connectionRequest.onRequestFinished(CSHttpConnection.this);
                 } catch (JSONException e) {
                     // Handle non-JSON response
-                    setError("Invalid JSON response");
+                    setError(ErrorMessages.INVALID_JSON_RESPONSE);
                 }
             } else {
                 assert response.errorBody() != null;
diff --git a/src/main/java/com/contentstack/sdk/ContentType.java b/src/main/java/com/contentstack/sdk/ContentType.java
index da2b8ba5..6607159f 100644
--- a/src/main/java/com/contentstack/sdk/ContentType.java
+++ b/src/main/java/com/contentstack/sdk/ContentType.java
@@ -40,7 +40,7 @@ public class ContentType {
     public JSONObject contentTypeData;
 
     protected ContentType() throws IllegalAccessException {
-        throw new IllegalAccessException("Can Not Access Private Modifier");
+        throw new IllegalAccessException(ErrorMessages.DIRECT_INSTANTIATION_CONTENT_TYPE);
     }
 
     protected ContentType(String contentTypeUid) {
@@ -158,7 +158,7 @@ public void fetch(@NotNull JSONObject params, final ContentTypesCallback callbac
         }
         params.put("environment", headers.get("environment"));
         if (contentTypeUid == null || contentTypeUid.isEmpty()) {
-            throw new IllegalAccessException("contentTypeUid is required");
+            throw new IllegalAccessException(ErrorMessages.CONTENT_TYPE_UID_REQUIRED);
         }
         fetchContentTypes(urlString, params, headers, callback);
     }
diff --git a/src/main/java/com/contentstack/sdk/ContentTypesModel.java b/src/main/java/com/contentstack/sdk/ContentTypesModel.java
index 05332b84..65cafd58 100644
--- a/src/main/java/com/contentstack/sdk/ContentTypesModel.java
+++ b/src/main/java/com/contentstack/sdk/ContentTypesModel.java
@@ -29,7 +29,7 @@ public void setJSON(JSONObject responseJSON) {
                 try {
                     this.response = new JSONObject((LinkedHashMap<?, ?>) responseJSON.get(ctKey));
                 } catch (Exception e) {
-                    System.err.println("Error processing 'content_type': " + e.getMessage());
+                    System.err.println(ErrorMessages.INVALID_CONTENT_TYPE_DATA + " Technical details: " + e.getMessage());
                 }
             }
             String ctListKey = "content_types";
@@ -44,14 +44,14 @@ public void setJSON(JSONObject responseJSON) {
                             JSONObject jsonModel = new JSONObject((LinkedHashMap<?, ?>) model);
                             objectList.add(jsonModel);
                         } else {
-                            System.err.println("Invalid type in 'content_types' list. Expected LinkedHashMap.");
+                            System.err.println(ErrorMessages.INVALID_CONTENT_TYPES_LIST);
                         }
                     });
                 }
                 this.response = new JSONArray(objectList);
                 this.responseJSONArray = new JSONArray(objectList);
             } catch (Exception e) {
-            System.err.println("Error processing 'content_types': " + e.getMessage());
+            System.err.println(ErrorMessages.INVALID_CONTENT_TYPE_DATA + " Technical details: " + e.getMessage());
         }
       }
     }
diff --git a/src/main/java/com/contentstack/sdk/Contentstack.java b/src/main/java/com/contentstack/sdk/Contentstack.java
index 7154df8a..b287be16 100644
--- a/src/main/java/com/contentstack/sdk/Contentstack.java
+++ b/src/main/java/com/contentstack/sdk/Contentstack.java
@@ -19,7 +19,7 @@ public class Contentstack {
 
     // Modifier Protected
     protected Contentstack() throws IllegalAccessException {
-        throw new IllegalAccessException("Can Not Access Private Modifier");
+        throw new IllegalAccessException(ErrorMessages.DIRECT_INSTANTIATION_CONTENTSTACK);
     }
 
     /**
@@ -88,13 +88,13 @@ private static void validateCredentials(String stackApiKey, String deliveryToken
         Objects.requireNonNull(environment, "Environment can not be null");
 
         if (stackApiKey.isEmpty()) {
-            throw new IllegalAccessException("API Key can not be empty");
+            throw new IllegalAccessException(ErrorMessages.MISSING_API_KEY);
         }
         if (deliveryToken.isEmpty()) {
-            throw new IllegalAccessException("Delivery Token can not be empty");
+            throw new IllegalAccessException(ErrorMessages.MISSING_DELIVERY_TOKEN);
         }
         if (environment.isEmpty()) {
-            throw new IllegalAccessException("Environment can not be empty");
+            throw new IllegalAccessException(ErrorMessages.MISSING_ENVIRONMENT);
         }
     }
 
diff --git a/src/main/java/com/contentstack/sdk/EntriesModel.java b/src/main/java/com/contentstack/sdk/EntriesModel.java
index ff9a68c7..94995ee8 100644
--- a/src/main/java/com/contentstack/sdk/EntriesModel.java
+++ b/src/main/java/com/contentstack/sdk/EntriesModel.java
@@ -33,7 +33,7 @@ protected EntriesModel(JSONObject responseJSON) {
             }
         } catch (Exception e) {
             Logger logger = Logger.getLogger(EntriesModel.class.getSimpleName());
-            logger.log(Level.SEVERE, e.getLocalizedMessage(), e);
+            logger.log(Level.SEVERE, ErrorMessages.ENTRIES_PROCESSING_FAILED, e);
         }
 
     }
diff --git a/src/main/java/com/contentstack/sdk/Entry.java b/src/main/java/com/contentstack/sdk/Entry.java
index f762aebc..ab24592e 100644
--- a/src/main/java/com/contentstack/sdk/Entry.java
+++ b/src/main/java/com/contentstack/sdk/Entry.java
@@ -45,7 +45,7 @@ public class Entry {
     protected String rteContent = null;
 
     protected Entry() throws IllegalAccessException {
-        throw new IllegalAccessException("Can Not Access Private Modifier");
+        throw new IllegalAccessException(ErrorMessages.DIRECT_INSTANTIATION_ENTRY);
     }
 
     protected Entry(String contentTypeName) {
@@ -503,7 +503,7 @@ public Calendar getDate(@NotNull String key) {
             String value = getString(key);
             return Constants.parseDate(value, null);
         } catch (Exception e) {
-            logger.log(Level.SEVERE, e.getLocalizedMessage(), e);
+            logger.log(Level.SEVERE, ErrorMessages.INVALID_DATE_FORMAT, e);
         }
         return null;
     }
@@ -525,7 +525,7 @@ public Calendar getCreateAt() {
             String value = getString("created_at");
             return Constants.parseDate(value, null);
         } catch (Exception e) {
-            logger.log(Level.SEVERE, e.getLocalizedMessage(), e);
+            logger.log(Level.SEVERE, ErrorMessages.INVALID_DATE_FORMAT, e);
         }
         return null;
     }
@@ -562,7 +562,7 @@ public Calendar getUpdateAt() {
             String value = getString("updated_at");
             return Constants.parseDate(value, null);
         } catch (Exception e) {
-            logger.log(Level.SEVERE, e.getLocalizedMessage(), e);
+            logger.log(Level.SEVERE, ErrorMessages.INVALID_DATE_FORMAT, e);
         }
         return null;
     }
@@ -601,7 +601,7 @@ public Calendar getDeleteAt() {
             String value = getString("deleted_at");
             return Constants.parseDate(value, null);
         } catch (Exception e) {
-            logger.log(Level.SEVERE, e.getLocalizedMessage(), e);
+            logger.log(Level.SEVERE, ErrorMessages.INVALID_DATE_FORMAT, e);
         }
         return null;
     }
@@ -764,7 +764,7 @@ public List<Entry> getAllEntries(String refKey, String refContentType) {
                         entryInstance = contentType.stackInstance.contentType(refContentType).entry();
                     } catch (Exception e) {
                         entryInstance = new Entry(refContentType);
-                        logger.log(Level.SEVERE, e.getLocalizedMessage(), e);
+                        logger.log(Level.SEVERE, ErrorMessages.INVALID_DATE_FORMAT, e);
                     }
                     entryInstance.setUid(model.uid);
                     entryInstance.resultJson = model.jsonObject;
@@ -928,9 +928,9 @@ public Entry exceptWithReferenceUid(@NotNull List<String> fieldUid, @NotNull Str
     public void fetch(EntryResultCallBack callback) {
         if (uid.isEmpty()) { // throws IllegalAccessException if uid is Empty
             try {
-                throw new IllegalAccessException("Entry Uid is required");
+                throw new IllegalAccessException(ErrorMessages.ENTRY_UID_REQUIRED);
             } catch (IllegalAccessException e) {
-                logger.log(Level.SEVERE, e.getLocalizedMessage(), e);
+                logger.log(Level.SEVERE, ErrorMessages.ENTRY_FETCH_FAILED, e);
             }
         }
         String urlString = "content_types/" + contentTypeUid + "/entries/" + uid;
diff --git a/src/main/java/com/contentstack/sdk/ErrorMessages.java b/src/main/java/com/contentstack/sdk/ErrorMessages.java
new file mode 100644
index 00000000..80739cc1
--- /dev/null
+++ b/src/main/java/com/contentstack/sdk/ErrorMessages.java
@@ -0,0 +1,76 @@
+package com.contentstack.sdk;
+
+/**
+ * Centralized error messages for the Contentstack SDK.
+ * This class contains all user-facing error messages to ensure consistency
+ * and make maintenance easier.
+ */
+public final class ErrorMessages {
+
+    // Prevent instantiation
+    private ErrorMessages() {
+        throw new UnsupportedOperationException("This is a utility class and cannot be instantiated");
+    }
+
+    // ========== AUTHENTICATION & ACCESS ERRORS ==========
+    
+    public static final String MISSING_API_KEY = "Missing API key. Provide a valid key from your Contentstack stack settings and try again.";
+    public static final String MISSING_DELIVERY_TOKEN = "Missing delivery token. Provide a valid token from your Contentstack stack settings and try again.";
+    public static final String MISSING_ENVIRONMENT = "Missing environment. Provide a valid environment name and try again.";
+    public static final String MISSING_REQUEST_HEADERS = "Missing request headers. Provide api_key, access_token, and environment, then try again.";
+    
+    // ========== DIRECT INSTANTIATION ERRORS ==========
+    
+    public static final String DIRECT_INSTANTIATION_STACK = "Direct instantiation of Stack is not allowed. Use Contentstack.stack() to create an instance.";
+    public static final String DIRECT_INSTANTIATION_CONTENTSTACK = "Direct instantiation of Stack is not allowed. Use Contentstack.stack() to create an instance.";
+    public static final String DIRECT_INSTANTIATION_CONTENT_TYPE = "Direct instantiation of ContentType is not allowed. Use Stack.contentType(uid) to create an instance.";
+    public static final String DIRECT_INSTANTIATION_ENTRY = "Direct instantiation of Entry is not allowed. Use ContentType.entry(uid) to create an instance.";
+    
+    // ========== REQUIRED FIELD ERRORS ==========
+    
+    public static final String CONTENT_TYPE_UID_REQUIRED = "Content type UID is required. Provide a valid UID and try again.";
+    public static final String ENTRY_UID_REQUIRED = "Missing entry UID. Provide a valid UID and try again.";
+    public static final String GLOBAL_FIELD_UID_REQUIRED = "Missing global field UID. Provide a valid UID and try again.";
+    
+    // ========== DATA VALIDATION ERRORS ==========
+    
+    public static final String INVALID_PARAMETER_KEY = "Invalid parameter key. Use only alphanumeric characters, underscores, and dots.";
+    public static final String INVALID_PARAMETER_VALUE = "Invalid parameter value. Remove unsupported characters and try again.";
+    public static final String INVALID_QUERY_URL = "Invalid query URL. Use a valid URL and try again.";
+    public static final String INVALID_DATE_FORMAT = "Invalid date format for field. Provide the date in ISO format and try again.";
+    
+    // ========== DATA TYPE ERRORS ==========
+    
+    public static final String INVALID_ASSETS_TYPE = "Invalid type for 'assets' key. Provide assets as a List or ArrayList and try again.";
+    public static final String INVALID_OBJECT_TYPE_ASSET_MODEL = "Invalid object type. Use an AssetModel object and try again.";
+    public static final String INVALID_CONTENT_TYPE_DATA = "Invalid content type data. Provide a LinkedHashMap structure and try again.";
+    public static final String INVALID_CONTENT_TYPES_LIST = "Invalid type in content types list. Use a LinkedHashMap and try again.";
+    public static final String INVALID_GLOBAL_FIELD_DATA = "Invalid global field data. Provide a LinkedHashMap structure and try again.";
+    public static final String INVALID_GLOBAL_FIELDS_LIST = "Invalid type in global fields list. Use a LinkedHashMap and try again.";
+    
+    // ========== MISSING DATA ERRORS ==========
+    
+    public static final String MISSING_ASSETS_LIST = "Missing assets list. Provide a valid list of assets and try again.";
+    public static final String MISSING_JSON_OBJECT_SYNC = "Missing JSON object for sync operation. Provide a valid JSON object with sync parameters and try again.";
+    
+    // ========== NETWORK & CONNECTION ERRORS ==========
+    
+    public static final String URL_PARAMETER_ENCODING_FAILED = "URL parameter encoding failed. Provide a valid key and value, then try again.";
+    public static final String LIVE_PREVIEW_URL_FAILED = "Failed to execute the Live Preview URL. Check your connection and try again.";
+    public static final String TAXONOMY_QUERY_FAILED = "Failed to execute taxonomy query. Check your network connection and verify taxonomy parameters.";
+    public static final String INVALID_JSON_RESPONSE = "Invalid JSON response. Check the server response format and try again.";
+    
+    // ========== CONFIGURATION ERRORS ==========
+    
+    public static final String MISSING_PREVIEW_TOKEN = "Missing preview token for rest-preview.contentstack.com. Set the preview token in your configuration to use Live Preview.";
+    public static final String LIVE_PREVIEW_NOT_ENABLED = "Live Preview is not enabled in the configuration. Enable it and try again.";
+    public static final String EMBEDDED_ITEMS_NOT_INCLUDED = "Embedded items are not included in the entry. Call includeEmbeddedItems() and try again.";
+    
+    // ========== OPERATION ERRORS ==========
+    
+    public static final String ENTRY_FETCH_FAILED = "Entry fetch operation failed due to missing UID. Provide a valid UID and try again.";
+    public static final String QUERY_EXECUTION_FAILED = "Query execution failed. Check the query and try again.";
+    public static final String ENTRIES_PROCESSING_FAILED = "Failed to process entries data. Check the entries format and try again.";
+    public static final String GROUP_DATE_PARSING_FAILED = "Failed to parse date from group field. Provide a valid date format and try again.";
+    public static final String QUERY_RESULT_PROCESSING_FAILED = "Failed to process query result data. Check the response format and try again.";
+}
diff --git a/src/main/java/com/contentstack/sdk/GlobalField.java b/src/main/java/com/contentstack/sdk/GlobalField.java
index 11901cff..196086bd 100644
--- a/src/main/java/com/contentstack/sdk/GlobalField.java
+++ b/src/main/java/com/contentstack/sdk/GlobalField.java
@@ -85,7 +85,7 @@ public GlobalField includeGlobalFieldSchema() {
     public void fetch(final GlobalFieldsCallback callback) throws IllegalAccessException {
         String urlString = "global_fields/" + globalFieldUid;
         if (globalFieldUid == null || globalFieldUid.isEmpty()) {
-            throw new IllegalAccessException("globalFieldUid is required");
+            throw new IllegalAccessException(ErrorMessages.GLOBAL_FIELD_UID_REQUIRED);
         }
         fetchGlobalFields(urlString, this.params, this.headers, callback);
     }
diff --git a/src/main/java/com/contentstack/sdk/GlobalFieldsModel.java b/src/main/java/com/contentstack/sdk/GlobalFieldsModel.java
index aad19e03..b8fce836 100644
--- a/src/main/java/com/contentstack/sdk/GlobalFieldsModel.java
+++ b/src/main/java/com/contentstack/sdk/GlobalFieldsModel.java
@@ -21,7 +21,7 @@ public void setJSON(JSONObject responseJSON) {
                 try {
                     this.response = new JSONObject((LinkedHashMap<?, ?>) responseJSON.get(gfKey));
                 } catch (Exception e) {
-                    System.err.println("Error processing 'global_field': " + e.getMessage());
+                    System.err.println(ErrorMessages.INVALID_GLOBAL_FIELD_DATA + " Technical details: " + e.getMessage());
                 }
             }
             String gfListKey = "global_fields";
@@ -36,14 +36,14 @@ public void setJSON(JSONObject responseJSON) {
                                 JSONObject jsonModel = new JSONObject((LinkedHashMap<?, ?>) model);
                                 objectList.add(jsonModel);
                             } else {
-                                System.err.println("Invalid type in 'global_fields' list. Expected LinkedHashMap.");
+                                System.err.println(ErrorMessages.INVALID_GLOBAL_FIELDS_LIST);
                             }
                         });
                     }
                     this.response = new JSONArray(objectList);
                     this.responseJSONArray = new JSONArray(objectList);
                 } catch (Exception e) {
-                    System.err.println("Error processing 'global_fields': " + e.getMessage());
+                    System.err.println(ErrorMessages.INVALID_GLOBAL_FIELD_DATA + " Technical details: " + e.getMessage());
                 }
             }
         }
diff --git a/src/main/java/com/contentstack/sdk/Group.java b/src/main/java/com/contentstack/sdk/Group.java
index 3dd575b9..c4081523 100644
--- a/src/main/java/com/contentstack/sdk/Group.java
+++ b/src/main/java/com/contentstack/sdk/Group.java
@@ -291,7 +291,7 @@ public Calendar getDate(String key) {
             String value = getString(key);
             return Constants.parseDate(value, null);
         } catch (Exception e) {
-            logger.log(Level.SEVERE, e.getLocalizedMessage(), e);
+            logger.log(Level.SEVERE, ErrorMessages.GROUP_DATE_PARSING_FAILED, e);
         }
         return null;
     }
diff --git a/src/main/java/com/contentstack/sdk/Query.java b/src/main/java/com/contentstack/sdk/Query.java
index b8774af4..fdc1f521 100644
--- a/src/main/java/com/contentstack/sdk/Query.java
+++ b/src/main/java/com/contentstack/sdk/Query.java
@@ -1235,7 +1235,7 @@ private void throwException(String queryName, String messageString, @Nullable Ex
         }
         errorHashMap.put("detail", messageString);
         assert e != null;
-        logger.log(Level.SEVERE, e.getLocalizedMessage(), e);
+        logger.log(Level.SEVERE, ErrorMessages.QUERY_EXECUTION_FAILED, e);
     }
 
     protected void setQueryJson() {
@@ -1430,7 +1430,8 @@ public Query includeReferenceContentTypUid() {
     public Query whereIn(@NotNull String key, Query queryObject) {
         if(isValidKey(key)){
             JSONObject inQueryObj = new JSONObject();
-            inQueryObj.put("$in_query", queryObject.queryValueJSON.toString());
+            JSONObject queryValue = new JSONObject(queryObject.queryValueJSON.toString());
+            inQueryObj.put("$in_query", queryValue);
             queryValueJSON.put(key, inQueryObj);
         } else {
             throwException("whereIn", "Invalid key", null);
@@ -1459,7 +1460,8 @@ public Query whereIn(@NotNull String key, Query queryObject) {
     public Query whereNotIn(@NotNull String key, Query queryObject) {
         if(isValidKey(key)){    
             JSONObject inQueryObj = new JSONObject();
-            inQueryObj.put("$nin_query", queryObject.queryValueJSON.toString());
+            JSONObject queryValue = new JSONObject(queryObject.queryValueJSON.toString());
+            inQueryObj.put("$nin_query", queryValue);
             queryValueJSON.put(key, inQueryObj);
         } else {
             throwException("whereNotIn", "Invalid key", null);
diff --git a/src/main/java/com/contentstack/sdk/QueryResult.java b/src/main/java/com/contentstack/sdk/QueryResult.java
index 4c44737a..d3097bb4 100644
--- a/src/main/java/com/contentstack/sdk/QueryResult.java
+++ b/src/main/java/com/contentstack/sdk/QueryResult.java
@@ -131,7 +131,7 @@ private void extractCount() {
     }
 
     private void logException(Exception e) {
-        logger.log(Level.SEVERE, e.getLocalizedMessage(), e);
+        logger.log(Level.SEVERE, ErrorMessages.QUERY_RESULT_PROCESSING_FAILED, e);
     }
 
 
diff --git a/src/main/java/com/contentstack/sdk/Stack.java b/src/main/java/com/contentstack/sdk/Stack.java
index b50ccb69..1de85031 100644
--- a/src/main/java/com/contentstack/sdk/Stack.java
+++ b/src/main/java/com/contentstack/sdk/Stack.java
@@ -39,7 +39,7 @@ public class Stack {
     protected JSONObject syncParams = null;
 
     protected Stack() throws IllegalAccessException {
-        throw new IllegalAccessException("Can Not Access Private Modifier");
+        throw new IllegalAccessException(ErrorMessages.DIRECT_INSTANTIATION_STACK);
     }
 
     protected Stack(@NotNull String apiKey) {
@@ -166,7 +166,7 @@ public Stack livePreviewQuery(Map<String, String> query) throws IOException {
 
         String livePreviewUrl = this.livePreviewEndpoint.concat(config.livePreviewContentType).concat("/entries/" + config.livePreviewEntryUid);
         if (livePreviewUrl.contains("/null/")) {
-            throw new IllegalStateException("Malformed Query Url");
+            throw new IllegalStateException(ErrorMessages.INVALID_QUERY_URL);
         }
         Response<ResponseBody> response = null;
         try {
@@ -178,14 +178,14 @@ public Stack livePreviewQuery(Map<String, String> query) throws IOException {
                 if(config.previewToken != null) { 
                     liveHeader.put("preview_token", config.previewToken);
                 } else{
-                    throw new IllegalAccessError("Provide the Preview Token for the host rest-preview.contentstack.com");
+                    throw new IllegalAccessError(ErrorMessages.MISSING_PREVIEW_TOKEN);
                 }
             } else { 
                 liveHeader.put("authorization", config.managementToken);
             }
             response = this.service.getRequest(livePreviewUrl, liveHeader).execute();
         } catch (IOException e) {
-            throw new IllegalStateException("IO Exception while executing the Live Preview url");
+            throw new IllegalStateException(ErrorMessages.LIVE_PREVIEW_URL_FAILED);
         }
         if (response.isSuccessful()) {
             assert response.body() != null;
@@ -196,7 +196,7 @@ public Stack livePreviewQuery(Map<String, String> query) throws IOException {
             }
         }
     } else { 
-        throw new IllegalStateException("Live Preview is not enabled in Config");
+        throw new IllegalStateException(ErrorMessages.LIVE_PREVIEW_NOT_ENABLED);
     }
         return this;
     }
@@ -618,7 +618,7 @@ public void updateAssetUrl(Entry entry) {
         JSONObject entryJson = entry.toJSON();
         // Check if entry consists of _embedded_items object
         if (!entryJson.has("_embedded_items")) {
-            throw new IllegalArgumentException("_embedded_items not present in entry. Call includeEmbeddedItems() before fetching entry.");
+            throw new IllegalArgumentException(ErrorMessages.EMBEDDED_ITEMS_NOT_INCLUDED);
         }
         // Get _embedded_items as a JSONObject
         JSONObject embeddedItems = entryJson.getJSONObject("_embedded_items");
diff --git a/src/main/java/com/contentstack/sdk/SyncStack.java b/src/main/java/com/contentstack/sdk/SyncStack.java
index b83fd862..0370d857 100755
--- a/src/main/java/com/contentstack/sdk/SyncStack.java
+++ b/src/main/java/com/contentstack/sdk/SyncStack.java
@@ -63,7 +63,7 @@ public List<JSONObject> getItems() {
 
     protected synchronized void setJSON(@NotNull JSONObject jsonobject) {
         if (jsonobject == null) {
-            throw new IllegalArgumentException("JSON object cannot be null.");
+            throw new IllegalArgumentException(ErrorMessages.MISSING_JSON_OBJECT_SYNC);
         }
     
         this.receiveJson = jsonobject;
diff --git a/src/test/java/com/contentstack/sdk/TestContentType.java b/src/test/java/com/contentstack/sdk/TestContentType.java
index 2948f9bf..731591ee 100644
--- a/src/test/java/com/contentstack/sdk/TestContentType.java
+++ b/src/test/java/com/contentstack/sdk/TestContentType.java
@@ -19,7 +19,7 @@ void testPrivateAccess() {
         try {
             new ContentType();
         } catch (IllegalAccessException e) {
-            Assertions.assertEquals("Can Not Access Private Modifier", e.getLocalizedMessage());
+            Assertions.assertEquals("Direct instantiation of ContentType is not allowed. Use Stack.contentType(uid) to create an instance.", e.getLocalizedMessage());
             logger.info("passed...");
         }
     }
diff --git a/src/test/java/com/contentstack/sdk/TestContentstack.java b/src/test/java/com/contentstack/sdk/TestContentstack.java
index 1a2fb41c..a5cf4f98 100644
--- a/src/test/java/com/contentstack/sdk/TestContentstack.java
+++ b/src/test/java/com/contentstack/sdk/TestContentstack.java
@@ -26,7 +26,7 @@ void initStackPrivateModifier() {
             new Contentstack();
         } catch (Exception e) {
             logger.info(e.getLocalizedMessage());
-            Assertions.assertEquals("Can Not Access Private Modifier", e.getLocalizedMessage());
+            Assertions.assertEquals("Direct instantiation of Stack is not allowed. Use Contentstack.stack() to create an instance.", e.getLocalizedMessage());
         }
     }
 
@@ -67,7 +67,7 @@ void initStackWithEmptyAPIKey() {
             Contentstack.stack("", DELIVERY_TOKEN, ENV);
         } catch (Exception e) {
             logger.info(e.getLocalizedMessage());
-            Assertions.assertEquals("API Key can not be empty", e.getLocalizedMessage(), "Set APIKey Null");
+            Assertions.assertEquals("Missing API key. Provide a valid key from your Contentstack stack settings and try again.", e.getLocalizedMessage(), "Set APIKey Null");
         }
     }
 
@@ -77,7 +77,7 @@ void initStackWithEmptyDeliveryToken() {
             Contentstack.stack(API_KEY, "", ENV);
         } catch (Exception e) {
             logger.info(e.getLocalizedMessage());
-            Assertions.assertEquals("Delivery Token can not be empty", e.getLocalizedMessage(),
+            Assertions.assertEquals("Missing delivery token. Provide a valid token from your Contentstack stack settings and try again.", e.getLocalizedMessage(),
                     "Set deliveryToken Null");
         }
     }
@@ -88,7 +88,7 @@ void initStackWithEmptyEnvironment() {
             Contentstack.stack(API_KEY, DELIVERY_TOKEN, "");
         } catch (Exception e) {
             logger.info(e.getLocalizedMessage());
-            Assertions.assertEquals("Environment can not be empty", e.getLocalizedMessage(), "Set Environment Null");
+            Assertions.assertEquals("Missing environment. Provide a valid environment name and try again.", e.getLocalizedMessage(), "Set Environment Null");
         }
     }
 
diff --git a/src/test/java/com/contentstack/sdk/TestEntry.java b/src/test/java/com/contentstack/sdk/TestEntry.java
index 044ab5e3..b3311e29 100644
--- a/src/test/java/com/contentstack/sdk/TestEntry.java
+++ b/src/test/java/com/contentstack/sdk/TestEntry.java
@@ -25,7 +25,7 @@ void entryCallingPrivateModifier() {
         try {
             new Entry();
         } catch (IllegalAccessException e) {
-            Assertions.assertEquals("Can Not Access Private Modifier", e.getLocalizedMessage());
+            Assertions.assertEquals("Direct instantiation of Entry is not allowed. Use ContentType.entry(uid) to create an instance.", e.getLocalizedMessage());
             logger.info("passed.");
         }
     }
diff --git a/src/test/java/com/contentstack/sdk/TestLivePreview.java b/src/test/java/com/contentstack/sdk/TestLivePreview.java
index 98342989..29ac41da 100644
--- a/src/test/java/com/contentstack/sdk/TestLivePreview.java
+++ b/src/test/java/com/contentstack/sdk/TestLivePreview.java
@@ -197,7 +197,7 @@ void testLivePreviewWithoutPreviewToken() throws Exception {
             stack.livePreviewQuery(hashMap);
         }, "Expected livePreviewQuery to throw IllegalAccessError");
 
-        Assertions.assertTrue(thrown.getMessage().contains("Provide the Preview Token for the host rest-preview.contentstack.com"), 
+        Assertions.assertTrue(thrown.getMessage().contains("Missing preview token for rest-preview.contentstack.com"), 
             "Exception message should mention that Preview Token is required");
 
         logger.severe(thrown.getMessage());  
@@ -220,7 +220,7 @@ void testLivePreviewDisabled() throws IllegalAccessException, IOException {
     });
 
     // Optionally, you can check the message of the exception
-    assertEquals("Live Preview is not enabled in Config", exception.getMessage(), 
+    assertEquals("Live Preview is not enabled in the configuration. Enable it and try again.", exception.getMessage(), 
                  "Expected exception message does not match");
     }
 
diff --git a/src/test/java/com/contentstack/sdk/TestStack.java b/src/test/java/com/contentstack/sdk/TestStack.java
index 48ae0ec2..d8a826b8 100644
--- a/src/test/java/com/contentstack/sdk/TestStack.java
+++ b/src/test/java/com/contentstack/sdk/TestStack.java
@@ -25,8 +25,8 @@ class TestStack {
     @Order(1)
     void stackExceptionTesting() {
         IllegalAccessException thrown = Assertions.assertThrows(IllegalAccessException.class, Stack::new,
-                "Can Not Access Private Modifier");
-        assertEquals("Can Not Access Private Modifier", thrown.getLocalizedMessage());
+                "Direct instantiation of Stack is not allowed. Use Contentstack.stack() to create an instance.");
+        assertEquals("Direct instantiation of Stack is not allowed. Use Contentstack.stack() to create an instance.", thrown.getLocalizedMessage());
     }
 
     @Test
@@ -35,7 +35,7 @@ void testStackInitThrowErr() {
         try {
             stack = new Stack();
         } catch (IllegalAccessException e) {
-            assertEquals("Can Not Access Private Modifier", e.getLocalizedMessage());
+            assertEquals("Direct instantiation of Stack is not allowed. Use Contentstack.stack() to create an instance.", e.getLocalizedMessage());
         }
     }