Update app.py

app.py

@@ -26,7 +26,7 @@ client = OpenAI(api_key=os.environ.get("OPENAI_API_KEY"))
 
 assistant, thread = None, None
 
-def today_tool() -> date:
+def today_tool() -> str:
     """Returns today's date. Use this function for any questions related to knowing today's date. 
        There is no input. This function always returns today's date."""
     return str(date.today())