400 Bad Request with Gemini: Function Parameter Validation Failure

[ryujim]

Describe the bug

When attempting to use Goose with Gemini as the provider, the session fails with a 400 Bad Request error related to function declarations parameter validation. The error specifically mentions that only 'enum' is supported for STRING type in the URL format specification.

Error message:

ERROR goose::agents::truncate: Error: Request failed: Request failed with status: 400 Bad Request. Message: * GenerateContentRequest.tools[0].function_declarations[4].parameters.properties[url].format: only 'enum' is supported for STRING type

    at crates/goose/src/agents/truncate.rs:279

To Reproduce

Steps to reproduce the behavior:

1. Start Goose session
2. Enter any input
3. Observe the error in the response

Expected behavior

The session should establish successfully and process the input without throwing parameter validation errors related to function declarations.

Screenshots

• OS & Arch: macOS (x86_64/Intel)
• Interface: CLI
• Version: v1.0.4
• Extensions enabled: git, memory, computercontroller, developer, fetch
• Provider & Model: Google - gemini-2.0-flash-exp

Additional context

Same error on other models from Google.

[salman1993]

If you disable the fetch tool, that should fix it.

Why you're seeing the error?
We found that the Google Gemini model fails with fetch tool because Gemini API doesn't fully support jsonschema, specifically:
fetch server uses format: uri for the url field here. Gemini only supports format: string so it fails in this case.

[ryujim]

It fixed it.
Thanks for the quick reply!