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

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

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.

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.

fix(provider): strip sibling fields for Gemini anyOf/oneOf schemas

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.

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"
  }
}
]

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

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

To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.

Navigation Menu

Repository navigation

Gemini: all requests fail due to anyOf schema in github_create_pull_request_review tool #14509

Bug Report

Description

Root Cause

Impact

Workaround

Expected Fix

Environment

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

Error

Root cause

Fix needed

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Gemini: all requests fail due to anyOf schema in github_create_pull_request_review tool #14509

Description

Bug Report

Description

Root Cause

Impact

Workaround

Expected Fix

Environment

Activity

github-actions commented on Feb 21, 2026

kuyavinny commented on Feb 22, 2026

OmerFarukOruc commented on Feb 22, 2026

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

Error

Root cause

Fix needed

shyuuuuni commented on Feb 23, 2026

RovshanMuradov commented on Feb 23, 2026

kuyavinny commented on Feb 24, 2026

github-actions commented on Apr 26, 2026

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions

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