** Please make sure you read the contribution guide and file the issues in the right place. **
Contribution guide.

Describe the bug
When I tried to edit an agent in builder mode in adk web, I got the following error:

adk_web_server.py:1431 - Error in event_generator: Failed to parse the parameter file_patterns: List[str] | None = None of function cleanup_unused_files for automatic function calling. Automatic function calling works best with simpler function signature schema, consider manually parsing your function declaration for function cleanup_unused_files.

I was not able to use the AI chat to interact with builder.

To Reproduce
Steps to reproduce the behavior:

1. Install adk.
2. run adk web
3. Open adk web editor, create a new agent.
4. Error in console: adk_web_server.py:1431 - Error in event_generator: Failed to parse the parameter file_patterns: List[str] | None = None of function cleanup_unused_files for automatic function calling. Automatic function calling works best with simpler function signature schema, consider manually parsing your function declaration for function cleanup_unused_files.

Expected behavior
I was expecting to use the assistant to create the agent.

Screenshots
N/A, no aparent error on the UI

Desktop (please complete the following information):

• OS: macOS
• Python version(python -V): 3.14
• ADK version(pip show google-adk): 1.18.0

Model Information:

• Are you using LiteLLM: No
• Which model is being used: gemini-2.5-flash

Additional context
N/A