Update app.py

made some change

app.py

@@ -20,9 +20,9 @@ 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_relevant_joke(keyword: str = None) -> str:
+def get_a_joke(keyword: str = None) -> str:
     """
-    Fetches a safe joke from the JokeAPI (v2.jokeapi.dev). 
+    A tool that fetches a joke.
     It can return either a single-part or a two-part joke.
 
     The joke can be optionally filtered by a keyword to provide some relevance.