diff --git a/Backend/tools-services/src/main/java/com/r11/tools/controller/XPathController.java b/Backend/tools-services/src/main/java/com/r11/tools/controller/XPathController.java
index f60a3d8..dbf3840 100644
--- a/Backend/tools-services/src/main/java/com/r11/tools/controller/XPathController.java
+++ b/Backend/tools-services/src/main/java/com/r11/tools/controller/XPathController.java
@@ -26,24 +26,31 @@ public class XPathController implements RestController {
         this.xalan = xalan;
     }
 
-    private XMLResponseBody prepareErrorResponse(String message, String processor) {
+    private XMLResponseBody errorResponse(String message, String processor) {
         return new XMLResponseBody(message, "ERR", processor, -1);
     }
 
+    private void nonValidEngineSelectedResponse(Response response) {
+        XMLResponseBody responseBody =
+                errorResponse("Valid engines are: saxon, xalan", "N/A");
+        response.body(this.gson.toJson(responseBody));
+        response.status(400);
+    }
+
     @ScopedControllerManifest(method = HandlerType.POST, path = "/xpath")
     public void acceptRequest(Request request, Response response) {
         XMLRequestBody requestBody;
         try {
             requestBody = this.gson.fromJson(request.body(), XMLRequestBody.class);
         } catch (Exception e) {
-            XMLResponseBody responseBody = prepareErrorResponse(e.getMessage(), "N/A");
+            XMLResponseBody responseBody = errorResponse(e.getMessage(), "N/A");
             response.status(400);
             response.body(this.gson.toJson(responseBody));
             return;
         }
 
         if (requestBody.getProcessor() == null) {
-            response.body("saxon, xalan");
+            nonValidEngineSelectedResponse(response);
             return;
         }
 
@@ -55,7 +62,7 @@ public class XPathController implements RestController {
                 process(response, requestBody, xalan);
                 break;
             default:
-                response.body("saxon, xalan");
+                nonValidEngineSelectedResponse(response);
         }
     }
 
@@ -74,7 +81,7 @@ public class XPathController implements RestController {
             responseBody.setType(xPathQueryResult.getType());
             this.logger.info("Request (XPath, " + engine.getVersion() + ") processed in " + duration + " ms.");
         } catch (Exception ex) {
-            responseBody = prepareErrorResponse(ex.getMessage(), engine.getVersion());
+            responseBody = errorResponse(ex.getMessage(), engine.getVersion());
             response.status(400);
 
             this.logger.error("Error on processing XPath using " + engine.getVersion() + ". " + ex);
diff --git a/Backend/tools-services/src/main/java/com/r11/tools/controller/XQueryController.java b/Backend/tools-services/src/main/java/com/r11/tools/controller/XQueryController.java
index 661ed37..dc38498 100644
--- a/Backend/tools-services/src/main/java/com/r11/tools/controller/XQueryController.java
+++ b/Backend/tools-services/src/main/java/com/r11/tools/controller/XQueryController.java
@@ -30,6 +30,13 @@ public class XQueryController implements RestController {
         return new XMLResponseBody(message, "ERR", processor, -1);
     }
 
+    private void nonValidEngineSelectedResponse(Response response) {
+        XMLResponseBody responseBody =
+                prepareErrorResponse("Valid engines are: saxon", "N/A");
+        response.body(this.gson.toJson(responseBody));
+        response.status(400);
+    }
+
     @ScopedControllerManifest(method = HandlerType.POST, path = "/xquery")
     public void acceptRequest(Request request, Response response) {
         XMLRequestBody requestBody;
@@ -44,10 +51,10 @@ public class XQueryController implements RestController {
         }
 
         try {
-            if (requestBody.getProcessor().equals("saxon"))
+            if (requestBody.getProcessor().equalsIgnoreCase("saxon"))
                 process(response, requestBody, saxon);
             else
-                response.body("saxon");
+                nonValidEngineSelectedResponse(response);
         } catch (Exception e) {
             XMLResponseBody responseBody = prepareErrorResponse(e.getMessage(), "Saxon");
 
diff --git a/Backend/tools-services/src/main/java/com/r11/tools/controller/XsdController.java b/Backend/tools-services/src/main/java/com/r11/tools/controller/XsdController.java
index 6fbfb1a..294c6dc 100644
--- a/Backend/tools-services/src/main/java/com/r11/tools/controller/XsdController.java
+++ b/Backend/tools-services/src/main/java/com/r11/tools/controller/XsdController.java
@@ -26,9 +26,16 @@ public class XsdController implements RestController {
     private XMLResponseBody prepareErrorResponse(String message, String processor) {
         return new XMLResponseBody(message, "ERR", processor, -1);
     }
+
+    private void nonValidEngineSelectedResponse(Response response) {
+        XMLResponseBody responseBody =
+                prepareErrorResponse("Valid engines is: xalan", "N/A");
+        response.body(this.gson.toJson(responseBody));
+        response.status(400);
+    }
     @ScopedControllerManifest(method = HandlerType.POST, path = "/xsd")
     public void acceptRequest(Request request, Response response) {
-        XMLRequestBody requestBody = null;
+        XMLRequestBody requestBody;
         try {
             requestBody = this.gson.fromJson(request.body(), XMLRequestBody.class);
         } catch (Exception e) {
@@ -36,13 +43,22 @@ public class XsdController implements RestController {
 
             response.status(400);
             response.body(this.gson.toJson(responseBody));
+            return;
         }
-        process(response, requestBody, xalan);
+
+        if (requestBody.getProcessor() == null) {
+            nonValidEngineSelectedResponse(response);
+            return;
+        }
+        if (requestBody.getProcessor().equalsIgnoreCase("xalan"))
+            process(response, requestBody, xalan);
+        else
+            nonValidEngineSelectedResponse(response);
 
     }
 
     private void process(Response response, XMLRequestBody requestBody, XmlEngine engine) {
-        XMLResponseBody responseBody;
+        XMLResponseBody responseBody = null;
         try {
             long timeStart = System.currentTimeMillis();
             String result = engine.validate(requestBody.getData(), requestBody.getProcess()).trim();
@@ -59,8 +75,11 @@ public class XsdController implements RestController {
 
             this.logger.error("Error on validation against XSD using " + engine.getVersion() + ". " + ex);
         }
+        finally {
+            response.body(this.gson.toJson(responseBody));
+        }
+
 
-        response.body(this.gson.toJson(responseBody));
     }
 
 }
diff --git a/Backend/tools-services/src/main/java/com/r11/tools/controller/XsltController.java b/Backend/tools-services/src/main/java/com/r11/tools/controller/XsltController.java
index 10d52a3..a2b7e95 100644
--- a/Backend/tools-services/src/main/java/com/r11/tools/controller/XsltController.java
+++ b/Backend/tools-services/src/main/java/com/r11/tools/controller/XsltController.java
@@ -28,6 +28,14 @@ public class XsltController implements RestController {
     private XMLResponseBody prepareErrorResponse(String message, String processor) {
         return new XMLResponseBody(message, "ERR", processor, -1);
     }
+
+    private void nonValidEngineSelectedResponse(Response response) {
+        XMLResponseBody responseBody =
+                prepareErrorResponse("Valid engines are: saxon, xalan", "N/A");
+        response.body(this.gson.toJson(responseBody));
+        response.status(400);
+    }
+
     @ScopedControllerManifest(method = HandlerType.POST, path = "/xslt")
     public void acceptRequest(Request request, Response response) {
         XMLRequestBody requestBody;
@@ -42,7 +50,7 @@ public class XsltController implements RestController {
         }
 
         if (requestBody.getProcessor() == null) {
-            response.body("saxon, xalan");
+            nonValidEngineSelectedResponse(response);
             return;
         }
 
@@ -56,7 +64,7 @@ public class XsltController implements RestController {
                 return;
 
             default:
-                response.body("saxon, xalan");
+                nonValidEngineSelectedResponse(response);
         }
     }