What is gmail-mcp CLAUDE.md?

A set of Claude Code instructions for working on a Gmail MCP server, including build commands, architecture, and its two-step login process.

Use it when developing or testing this Gmail server, especially its read-only Gmail access, label filtering, and OAuth login flow.

It gives the coding assistant repository-specific context so it can build, test, and modify the project consistently.

How SynclyAI/gmail-mcp configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to SynclyAI/gmail-mcp. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/SynclyAI/gmail-mcp/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/SynclyAI/gmail-mcp

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/synclyai/gmail-mcp/claude-md/github.svg)](https://agentmods.dev/instructions/synclyai/gmail-mcp/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/synclyai/gmail-mcp/claude-md"><img src="https://agentmods.dev/badge/instructions/synclyai/gmail-mcp/claude-md/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/synclyai/gmail-mcp/claude-md"><img src="https://agentmods.dev/badge/instructions/synclyai/gmail-mcp/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 628 This file is loaded in full into every session.

When invoked 628 The same file — it is already loaded in full.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00628	$0.00628
Opus 5.5	$0.00251	$0.00251
Sonnet 5.5	$0.00126	$0.00126
Haiku 4.5	$0.00063	$0.00063

Measured 2mo ago against content hash cf9b2c8ad496, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

gmail-mcp CLAUDE.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

CLAUDE.md · 58 lines

How it starts

The opening of the file, as written. The whole thing — 58 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Build and Test Commands

npm run build          # TypeScript compilation
npm test               # Run all tests
npm run test:watch     # Run tests in watch mode
npx vitest run src/auth/session.test.ts  # Run single test file
npm run dev            # Development mode with tsx watch
npm start              # Run compiled server

Architecture

Gmail MCP Server with read-only access and label-based filtering. Implements MCP SDK's OAuth 2.1 with PKCE for authentication.

Two-Tier OAuth Flow

The server bridges Google OAuth with MCP OAuth:

MCP Client → Server: Client initiates OAuth via mcpAuthRouter (standard MCP SDK flow)
Server → Google: GmailOAuthServerProvider.authorize() creates pending request, redirects to Google
Google → Server: /callback receives Google auth code, oauth-bridge.getRedirectUrl() exchanges it for tokens
Server → MCP Client: Returns MCP auth code, client exchanges for session token (used as bearer token)

Session token (not Google access token) is the MCP bearer token. Google tokens are stored server-side in SessionStore.

Key Components

src/index.ts - Express HTTPS server setup, registers routes
src/auth/gmail/oauth-provider.ts - GmailOAuthServerProvider implements MCP SDK's OAuthServerProvider, manages pending auth requests and auth codes
src/auth/gmail/oauth-handler.ts - Google OAuth operations (auth URL, token exchange, refresh)
src/auth/session.ts - SessionStore manages session lifecycle (temp → active), stores Google tokens
src/auth/routes.ts - OAuth endpoints via mcpAuthRouter, /callback for Google redirect
src/mcp/routes.ts - /mcp endpoint with bearer auth and labels middleware
src/mcp/server.ts - GmailMCPServer handles MCP tool requests
src/gmail/client.ts - GmailClient wraps Gmail API with label filtering

Label-Based Access Control

Read the full file on GitHub · 58 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 58 lines · 628 tokens per session scan A cf9b2c8ad496

Subscribe to this mod's changes

gmail-mcp CLAUDE.md is an instructions file published in the GitHub repository SynclyAI/gmail-mcp (1 stars, last pushed 9mo ago), licensed MIT. It adds 628 tokens to every session, about $0.0025 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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gmail-mcp: Instructions file for Claude Code