diff --git a/ml/thing.py b/ml/thing.py
index 3c92b6c1df8172c38e1382b1b9dd0e7a6ee95415..4fed98b8c18e0a95b2e2d44c2d19a59aaa46df2b 100644
--- a/ml/thing.py
+++ b/ml/thing.py
@@ -299,6 +299,7 @@ class Thing:
             value = self._uriToData(attribute_path)
         except KeyError:
             value = "invalid attribute path"
+            APP_LOGGER.critical(value)
 
         get_value_reply.fillGetValueReply(
             senderUUID=self.thing_id,
@@ -416,6 +417,7 @@ class Thing:
         )
         service_type = body_json.get("serviceType")
         parameters = body_json.get("parameters")
+        service_reply = ServiceReply()
         service_functionality = service_type.split('/')[0]
         service_functionality_obj = self.features.get(service_functionality)
         if service_functionality_obj is None:
@@ -423,46 +425,79 @@ class Thing:
                 "Functionality %s is not one of the built-in functionalities in %s!" % (
                     service_functionality, self.name)
             )
-        else:
-            # TODO: Call right functionality.
-            print(
-                BColors.OKBLUE
-                + "[S³I][Broker]"
-                + BColors.ENDC
-                + ": Execute the function {0} of the class {1}.".format(service_type.split('/')[1],
-                                                                       service_type.split('/')[0])
-            )
-            method = getattr(service_functionality_obj, service_type.split('/')[1])
-            result = method(**parameters)
-
-            if isinstance(result, bool):
-                result = {"ok": result}
-
-            service_reply = ServiceReply()
             service_reply.fillServiceReply(
                 senderUUID=self.thing_id,
                 receiverUUID=body_json.get("sender", None),
                 serviceType=body_json.get("serviceType", None),
-                results=result,
+                results={"error": "invalid functionalities (serviceType) {}".format(service_functionality)},
                 replyingToUUID=body_json.get("identifier", None),
                 msgUUID="s3i:{}".format(uuid.uuid4())
             )
 
-            res = self.broker.send(receiver_endpoints=[body_json.get("replyToEndpoint", None)],
-                                   msg=json.dumps(service_reply.msg))
-            if self.__is_broker_rest:
-                if res.status_code == 201:
-                    print(
-                        BColors.OKBLUE
-                        + "[S³I][Broker]"
-                        + BColors.ENDC
-                        + ": Send a S³I-B ServiceReply back to the requester  "
+        else:
+            # TODO: Call right functionality.
+            try:
+                method = getattr(service_functionality_obj, service_type.split('/')[1])
+            except AttributeError:
+                APP_LOGGER.critical(
+                    "Functionality %s is not one of the built-in functionalities in %s!" % (
+                        service_type.split('/')[1], self.name)
+                )
+                service_reply.fillServiceReply(
+                    senderUUID=self.thing_id,
+                    receiverUUID=body_json.get("sender", None),
+                    serviceType=body_json.get("serviceType", None),
+                    results={"error": "invalid functionalities (serviceType) {}".format(service_type.split('/')[1])},
+                    replyingToUUID=body_json.get("identifier", None),
+                    msgUUID="s3i:{}".format(uuid.uuid4())
+                )
+            else:
+                print(
+                    BColors.OKBLUE
+                    + "[S³I][Broker]"
+                    + BColors.ENDC
+                    + ": Execute the function {0} of the class {1}.".format(service_type.split('/')[1],
+                                                                            service_type.split('/')[0])
+                )
+                try:
+                    result = method(**parameters)
+                except TypeError:
+                    APP_LOGGER.critical("Invalid function arguments")
+                    service_reply.fillServiceReply(
+                        senderUUID=self.thing_id,
+                        receiverUUID=body_json.get("sender", None),
+                        serviceType=body_json.get("serviceType", None),
+                        results={"error": "invalid function arguments (parameters)"},
+                        replyingToUUID=body_json.get("identifier", None),
+                        msgUUID="s3i:{}".format(uuid.uuid4())
                     )
                 else:
-                    print( BColors.OKBLUE
-                        + "[S³I][Broker]"
-                        + BColors.ENDC
-                        + res.text)
+                    if isinstance(result, bool):
+                        result = {"ok": result}
+                    service_reply.fillServiceReply(
+                        senderUUID=self.thing_id,
+                        receiverUUID=body_json.get("sender", None),
+                        serviceType=body_json.get("serviceType", None),
+                        results=result,
+                        replyingToUUID=body_json.get("identifier", None),
+                        msgUUID="s3i:{}".format(uuid.uuid4())
+                    )
+
+        res = self.broker.send(receiver_endpoints=[body_json.get("replyToEndpoint", None)],
+                               msg=json.dumps(service_reply.msg))
+        if self.__is_broker_rest:
+            if res.status_code == 201:
+                print(
+                    BColors.OKBLUE
+                    + "[S³I][Broker]"
+                    + BColors.ENDC
+                    + ": Send a S³I-B ServiceReply back to the requester  "
+                )
+            else:
+                print( BColors.OKBLUE
+                    + "[S³I][Broker]"
+                    + BColors.ENDC
+                    + res.text)
 
     def on_get_value_reply(self, msg):
         print(