set up a conventional loop between assistant and tools

app.py

@@ -65,7 +65,7 @@ class BasicAgent:
         return final_answer, result["messages"]
 
     def assistant(self, state: State):
-        # System message
+        messages = state.get("messages", [])
         textual_description_of_tool="""
             search_tool(question: str, max_length: int = 1024) -> str:
                 Search info in the web.
@@ -86,11 +86,8 @@ class BasicAgent:
             content=f"""You are a general AI assistant. I will ask you a question. Report your thoughts, and finish your answer with the following template: FINAL ANSWER: [YOUR FINAL ANSWER]. YOUR FINAL ANSWER should be a number OR as few words as possible OR a comma separated list of numbers and/or strings. If you are asked for a number, don't use comma to write your number neither use units such as $ or percent sign unless specified otherwise. If you are asked for a string, don't use articles, neither abbreviations (e.g. for cities), and write the digits in plain text unless specified otherwise. If you are asked for a comma separated list, apply the above rules depending of whether the element to be put in the list is a number or a string. 
             You can use provided tools:\n{textual_description_of_tool}"""
         )
-    
-        return {
-            "messages": [self.model_with_tools.invoke([sys_msg] + state.get("messages", []))],
-            "question": state["question"]
-        }
+        new_message = self.model_with_tools.invoke([sys_msg] + messages)
+        return add_messages(state, [new_message])
 
     def search_tool(self, question: str, max_length: int = 1024) -> str:
         """