Gemini: all requests fail due to anyOf schema in github_create_pull_request_review tool

[IamCooller]

Bug Report

Description

When using Gemini as the AI provider in OpenCode, every request fails with the following error:

Unable to submit request because `github_create_pull_request_review` functionDeclaration
`parameters.comments` schema specified other fields alongside any_of.
When using any_of, it must be the only field set.
Learn more: https://cloud.google.com/vertex-ai/generative-ai/docs/multimodal/function-calling

Root Cause

Gemini API validates all tool schemas before processing any request.
The github_create_pull_request_review tool from @modelcontextprotocol/server-github
defines the comments parameter with anyOf combined with other fields (e.g. type, description, items).

Gemini strictly requires that when anyOf is used, it must be the only field in the schema object. No sibling fields allowed.

Impact

• ANY request to Gemini fails — not just GitHub-related ones
• The error appears even for simple questions like "hello"
• Makes Gemini completely unusable when the GitHub MCP server is enabled

Workaround

Disable the GitHub MCP server in opencode.json:

"github": {
  "enabled": false
}

Expected Fix

OpenCode should sanitize tool schemas before sending them to Gemini. When a schema uses anyOf, strip all sibling fields:

// Before (breaks Gemini):
{ type: 'array', anyOf: [...], description: '...' }

// After (Gemini-compatible):
{ anyOf: [...] }

Reference: https://cloud.google.com/vertex-ai/generative-ai/docs/multimodal/function-calling

Environment

• OpenCode with Gemini provider (via opencode-gemini-auth plugin)
• GitHub MCP: @modelcontextprotocol/server-github
• Platform: macOS

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Gemini: sanitizeGemini doesn't handle anyOf/const patterns in MCP tool schemas #12908: Gemini sanitizeGemini doesn't handle anyOf/const patterns in MCP tool schemas — very similar root cause (Gemini rejecting tool schemas with anyOf patterns), though targeting a slightly different schema pattern
• [bug] Gemini schema sanitization misses properties/required when type is undefined #13148: Gemini schema sanitization misses properties/required when type is undefined — also about gaps in sanitizeGemini

If your issue is distinct from the above (e.g. specifically about sibling fields alongside anyOf rather than anyOf/const flattening), please clarify the difference so this can be tracked separately.

[kuyavinny]

Same issue affects built-in edit tool — not MCP-specific

I'm encountering the identical error with OpenCode's built-in edit tool, not an MCP tool:

Error: Bad Request: {
  "error": {
    "code": 400,
    "message": "Unable to submit request because edit functionDeclaration parameters.edits schema specified other fields alongside any_of. When using any_of, it must be the only field set.",
    "status": "INVALID_ARGUMENT"
  }
}

This makes all Google/Gemini models completely unusable via the Antigravity auth plugin, since the edit tool is registered for every session.
This confirms the issue isn't limited to MCP tools — it also affects core built-in tools. The schema sanitization fix would need to handle all tools, not just MCP-sourced ones.

[OmerFarukOruc]

Additional findings: built-in edit tool schema causes failure, not MCP tools

Disabling MCP servers does not fix this. The failing tool is OpenCode's own built-in edit tool (function_declarations[5]), not a GitHub or any other MCP tool.

Error

GenerateContentRequest.tools[0].function_declarations[5].parameters.properties[edits].items.properties: only allowed for OBJECT type
GenerateContentRequest.tools[0].function_declarations[5].parameters.properties[edits].items.required: only allowed for OBJECT type

Root cause

The edit tool's edits parameter is an array whose items define properties and required fields, but without type: "object". Gemini's API strictly requires type: "object" to be set before allowing properties/required on any schema node.

Since Gemini validates all tool schemas upfront, this causes every request to fail — including simple "hello" messages.

Fix needed

The Gemini schema sanitizer needs to handle array items — when items contain properties/required, add type: "object" if missing. PRs #13666 and #12911 are on the right track but need to cover the items case as well.

[shyuuuuni]

I have same issue. Is there a solution? I'm using gemini as my main model.

Bad Request: [{
  "error": {
    "code": 400,
    "message": "Unable to submit request because `edit` functionDeclaration `parameters.edits` schema specified other fields alongside any_of. When using any_of, it must be the only field set. Learn more: https://cloud.google.com/vertex-ai/generative-ai/docs/multimodal/function-calling",
    "errors": [
      {
        "message": "Unable to submit request because `edit` functionDeclaration `parameters.edits` schema specified other fields alongside any_of. When using any_of, it must be the only field set. Learn more: https://cloud.google.com/vertex-ai/generative-ai/docs/multimodal/function-calling",
        "domain": "global",
        "reason": "badRequest"
      }
    ],
    "status": "INVALID_ARGUMENT"
  }
}
]

[RovshanMuradov]

I have same issue. Is there a solution? I'm using gemini as my main model.

Bad Request: [{
  "error": {
    "code": 400,
    "message": "Unable to submit request because `edit` functionDeclaration `parameters.edits` schema specified other fields alongside any_of. When using any_of, it must be the only field set. Learn more: https://cloud.google.com/vertex-ai/generative-ai/docs/multimodal/function-calling",
    "errors": [
      {
        "message": "Unable to submit request because `edit` functionDeclaration `parameters.edits` schema specified other fields alongside any_of. When using any_of, it must be the only field set. Learn more: https://cloud.google.com/vertex-ai/generative-ai/docs/multimodal/function-calling",
        "domain": "global",
        "reason": "badRequest"
      }
    ],
    "status": "INVALID_ARGUMENT"
  }
}
]

set this plugin with that pr and it will fix, until then we have to wait when Dax fixes it jenslys/opencode-gemini-auth#58

[kuyavinny]

I have PR #14659. It worked for me, but it needs more testing. It strips all sibling fields before submitting to the AI.