Update app.py

app.py

@@ -20,7 +20,7 @@ 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_calories(meal:str) -> str:
+def get_calories(meal:str) -> Union[str, None]:
     search_url = f"https://world.openfoodfacts.org/cgi/search.pl"
     params = {
          'search_terms': meal,