Update app.py

app.py

@@ -39,7 +39,7 @@ def yf_download_tool(ticker: str, start_date: date, end_date: date) -> pd.DataFr
        Use this function for any questions related to getting historical stock data. 
        The input should be a ticker string, a start date, and an end date. 
        This function always returns a pandas DataFrame."""
-    return yf.download(tickers, start=start_date, end=end_date)
+    return yf.download(ticker, start=start_date, end=end_date)
 
 tools = {
     "today_tool": today_tool,