ChatGPT Review for Claude

Get a second opinion from ChatGPT without leaving Claude Desktop.

This is a small local MCP server. It adds two tools to Claude:

It works through the OpenAI Codex CLI, so it uses your ChatGPT subscription. You don't need an API key.

Example prompt in Claude: "Draft the Q4 update, then ask ChatGPT to review it for clarity for executives and fix anything it flags."

Before you use this at work: everything you send through these tools (the document, focus, rubric, question and context) goes to OpenAI and is handled under your ChatGPT account's terms and data settings. Check that your company's AI policy allows sharing that material with OpenAI. If in doubt, don't send confidential, customer or personal data.

1. Install and sign in to Codex (one time)

You need Node.js 18 or later.

npm install -g @openai/codex
codex login          # choose "Sign in with ChatGPT"
codex exec --skip-git-repo-check "say hi"   # quick check

Related MCP server: chatgpt-interlocutor

2. Add it to Claude Desktop

Option A: extension file (easiest)

1. Download codex-review-mcp.mcpb from this repo's Releases page.

2. In Claude Desktop, open Settings → Extensions → Advanced settings → Install Extension… and choose the file. Double-clicking the file also works.

3. Leave Codex executable blank unless Claude can't find codex (see Troubleshooting).

Option B: config file

Open Settings → Developer → Edit Config. That opens claude_desktop_config.json:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

• Windows: %APPDATA%\Claude\claude_desktop_config.json

Add the server, then fully quit and reopen Claude.

Until this package is on npm, clone the repo and build it with npm ci && npm run build. Then point Claude at it:

macOS

{
  "mcpServers": {
    "chatgpt-review": {
      "command": "node",
      "args": ["/Users/YOU/codex-review-mcp/dist/index.js"],
      "env": { "CODEX_PATH": "/opt/homebrew/bin/codex" }
    }
  }
}

Windows

{
  "mcpServers": {
    "chatgpt-review": {
      "command": "node",
      "args": ["C:\\Users\\YOU\\codex-review-mcp\\dist\\index.js"],
      "env": { "CODEX_PATH": "C:\\Users\\YOU\\AppData\\Roaming\\npm\\codex.cmd" }
    }
  }
}

CODEX_PATH is optional. Run which codex (macOS) or where codex (Windows) to find the right value. If Claude says it can't find node, use its full path: /opt/homebrew/bin/node or C:\Program Files\nodejs\node.exe.

Settings

Set these as environment variables, or in the extension's settings.

Limits

• Your ChatGPT plan's limits apply. Each call counts as one Codex task against your plan's Codex usage limits. Heavy use can hit the plan's rate limit, so wait or upgrade the plan.

• Speed: a review usually takes 15–60 seconds, and long documents take longer. Calls stop after the timeout.

• Size: inputs above CODEX_REVIEW_MAX_CHARS are rejected. Send the relevant section instead.

• Text only. Claude passes the document as text. Paste or extract text from PDFs, slides and images first.

Does it work in Claude's Cowork (work) mode?

Short answer: it works in normal Claude Desktop chat. In Cowork, it only works for sessions that run on your computer, and new Cowork sessions now run in the cloud by default.

What Anthropic's documentation says (checked October 2026):

• Local MCP servers and .mcpb desktop extensions run only in the Claude Desktop app, not on the web or mobile (When to use desktop and web connectors; Getting started with local MCP servers).

• Cowork sessions run in the cloud by default. "Local MCP servers don't run in sessions in the cloud." Local Cowork sessions, where local MCP servers do load, remain for existing desktop deployments. On Pro and Max, that means only tasks started on the device before 6 October 2026 (Claude Cowork architecture overview).

• The plugin support table says local MCP servers, including .mcpb bundles, "load when the Cowork session runs on your computer" (Plugin feature support across platforms).

• On company-managed Macs and PCs, admins can turn these off with the MDM keys isLocalDevMcpEnabled (local MCP servers) and isDesktopExtensionEnabled (.mcpb extensions) (Enterprise configuration: MCP, plugins, skills, and hooks). If the install option is missing or greyed out, IT has probably disabled it.

So: use it from a regular chat in Claude Desktop. To use ChatGPT in cloud Cowork, you'd need a hosted (remote) connector. That would also need its own OpenAI credentials, which this project deliberately avoids.

Troubleshooting

How it works and safety

• Each call runs codex exec --skip-git-repo-check --sandbox read-only --ephemeral in a fresh, empty temporary folder. That folder is deleted afterwards, along with the answer file Codex writes there (--output-last-message). The reviewer prompt also tells ChatGPT not to run commands or edit files.

• The document goes to Codex on stdin, never on the command line. Processes start without a shell, so document text can't be interpreted as commands. On Windows, the server runs the codex.exe that npm installs behind its codex.cmd wrapper. If it can't find that file, it falls back to cmd.exe with only fixed, validated arguments.

• --ephemeral means Codex doesn't save the session on disk. OpenAI still receives and processes the content.

Development

npm ci
npm test            # unit + MCP protocol tests with a fake codex (no network)
npm run e2e         # real review through your logged-in codex
npm run pack:mcpb   # builds codex-review-mcp.mcpb

CI runs the tests on Ubuntu, macOS and Windows. Pushing a v* tag builds the .mcpb and attaches it to a GitHub release.

MIT licence.