[BUG] Gmail MCP Sever returns permission error on all tools

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The Gmail MCP server at gmailmcp.googleapis.com/mcp/v1 returns "caller does not have permission" on all tools despite valid OAuth with full scopes.

What Should Happen?

I should be able to authenticate against Gmail MCP using OAuth and be able to use the MCP tools to work with my gmail account.

Error Messages/Logs

"caller does not have permission"

Steps to Reproduce

1. Launch Claude code
2. Add Gmail MCP server
3. Authenticate via OAuth
4. Check that Claude Code is in the list of authenticated apps here: https://myaccount.google.com/connections
5. Then run a simple query in Claude "Get my last 10 emails" and notice that claude gets the permission error ("caller does not have permission")

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.139

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_