update readme

Author: tommaso-moro

README.md

@@ -1160,6 +1160,12 @@ Possible options:
 -   **list_copilot_spaces** - List Copilot Spaces
 </details>
 
+<summary>Web Search</summary>
+
+-   **web_search** - Web Search
+    -   `query`: A natural language query representing what to search for on the web. (string, required)
+</details>
+
 ## Dynamic Tool Discovery
 
 **Note**: This feature is currently in beta and may not be available in all environments. Please test it out and let us know if you encounter any issues.