diff --git a/autogen/agentchat/contrib/agent_builder.py b/autogen/agentchat/contrib/agent_builder.py
index 7eaec3eef747..eba0b72c7942 100644
--- a/autogen/agentchat/contrib/agent_builder.py
+++ b/autogen/agentchat/contrib/agent_builder.py
@@ -182,7 +182,7 @@ class AgentBuilder:
     {agent_details}
 
     Hint:
-    # Only respond with the name of the agent that is most suited to execute the function and nothing else.
+    # Only respond with the name of the agent that is most suited to execute the function and nothing else.if there is no agent that is most suited to execute the function, respond with exectly"None"
     """
 
     UPDATED_AGENT_SYSTEM_MESSAGE = """
@@ -730,7 +730,7 @@ def _build_agents(
 
             if list_of_functions:
                 for func in list_of_functions:
-                    resp = (
+                    perferred_agent_name = (
                         self.builder_model.create(
                             messages=[
                                 {
@@ -747,28 +747,30 @@ def _build_agents(
                         .choices[0]
                         .message.content
                     )
+                    if perferred_agent_name in self.agent_procs_assign.keys():
+                        autogen.agentchat.register_function(
+                            func["function"],
+                            caller=self.agent_procs_assign[perferred_agent_name][0],
+                            executor=agent_list[0],
+                            name=func["name"],
+                            description=func["description"],
+                        )
 
-                    autogen.agentchat.register_function(
-                        func["function"],
-                        caller=self.agent_procs_assign[resp][0],
-                        executor=agent_list[0],
-                        name=func["name"],
-                        description=func["description"],
-                    )
-
-                    agents_current_system_message = [
-                        agent["system_message"] for agent in agent_configs if agent["name"] == resp
-                    ][0]
+                        agents_current_system_message = [
+                            agent["system_message"] for agent in agent_configs if agent["name"] == perferred_agent_name
+                        ][0]
 
-                    self.agent_procs_assign[resp][0].update_system_message(
-                        self.UPDATED_AGENT_SYSTEM_MESSAGE.format(
-                            agent_system_message=agents_current_system_message,
-                            function_name=func["name"],
-                            function_description=func["description"],
+                        self.agent_procs_assign[perferred_agent_name][0].update_system_message(
+                            self.UPDATED_AGENT_SYSTEM_MESSAGE.format(
+                                agent_system_message=agents_current_system_message,
+                                function_name=func["name"],
+                                function_description=func["description"],
+                            )
                         )
-                    )
 
-                    print(f"Function {func['name']} is registered to agent {resp}.")
+                        print(f"Function {func['name']} is registered to agent {perferred_agent_name}.")
+                    else:
+                        logger.debug(f"Function {func['name']} is not registered to any agent.")
 
         return agent_list, self.cached_configs.copy()