Update docstring

app.py

@@ -20,7 +20,7 @@ def my_cutom_tool(arg1:str, arg2:int)-> str: #it's import to specify the return
 
 @tool
 def fetch_binance_price(symbol: str = "BTCUSDT") -> str:
-    """Get price for a token from binance exchange
+    """Get price for a trading pair symbol from binance exchange
     Args:
         symbol: Trading pair symbol (e.g. 'BTCUSDT')
     """