Update app.py

I add a tool to do a simply calculation.

app.py

@@ -9,14 +9,20 @@ from Gradio_UI import GradioUI
 
 # Below is an example of a tool that does nothing. Amaze us with your creativity !
 @tool
-def my_custom_tool(arg1:str, arg2:int)-> str: #it's import to specify the return type
+def my_custom_tool(arg1:int, arg2:int)-> int: #it's import to specify the return type
     #Keep this format for the description / args / args description but feel free to modify the tool
-    """A tool that does nothing yet 
+    """A tool that do a simple calculation to multiply two numbers. 
     Args:
         arg1: the first argument
         arg2: the second argument
     """
-    return "What magic will you build ?"
+    try:
+        # to create a variable to store the calculation results
+        results = arg1 * arg2
+        return f"When we use {arg1} times {arg2}, we will get {results}"
+    except Exception as e:
+        return f"Error reporting when multiply {arg1} and {arg2}:{str(e)}
+   
 
 @tool
 def get_current_time_in_timezone(timezone: str) -> str: