type hint fix

app.py

@@ -19,7 +19,7 @@ def my_custom_tool(arg1:str, arg2:int)-> str: #it's import to specify the return
     return "What magic will you build ?"
 
 @tool
-def get_a_joke():
+def get_a_joke() -> str:
     """A tool to return a joke.
     """
     return "Why did the DevOps engineer break up with the cloud?,Because it kept throwing unexpected bills!😆"