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OpenAI Codex

OpenAI Codex CLI is OpenAI’s command-line coding assistant. This guide shows how to route Codex’s MCP connections through Maybe Don’t.

Prerequisites

  • Maybe Don’t running (see Agents overview)
  • OpenAI Codex CLI installed
  • A GitHub Personal Access Token

Configure Codex

Codex uses TOML configuration at ~/.codex/config.toml. Add the MCP server configuration:

[mcp_servers.maybe-dont]
url = "http://localhost:8080/mcp"
env_http_headers = { "X-GitHub-Token" = "GITHUB_TOKEN" }

The env_http_headers field maps header names to environment variable names. Codex reads the value of GITHUB_TOKEN from your environment and sends it as the X-GitHub-Token header.

Set Environment Variables

Before starting Codex, set your GitHub token:

export GITHUB_TOKEN="ghp_your_token_here"

Start Codex

Start Codex normally:

codex

Verify the Connection

In your Codex session, you should see GitHub tools prefixed with github__.

Test the gateway independently:

curl -s http://localhost:8080/mcp \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc": "2.0", "method": "tools/list", "id": 1}' | head -c 200

If you see a JSON response with tool definitions, the gateway is working.

Static Headers

If you prefer to hardcode the token (not recommended for secrets):

[mcp_servers.maybe-dont]
url = "http://localhost:8080/mcp"
http_headers = { "X-GitHub-Token" = "ghp_your_token_here" }
Security note: Prefer env_http_headers over http_headers for tokens and secrets. Static headers are stored in plain text.

What’s Happening

When Codex calls a tool:

  1. Codex sends the request to localhost:8080/mcp with your GitHub token
  2. The gateway validates the request using configured policies
  3. If allowed, the gateway forwards to GitHub
  4. All activity is logged to the audit log

Troubleshooting

Connection issues 

# Test the gateway is running
curl http://localhost:8080/mcp -X POST \
  -H "Content-Type: application/json" \
  -H "X-GitHub-Token: $GITHUB_TOKEN" \
  -d '{"jsonrpc":"2.0","method":"tools/list","id":1}'

Authentication errors

Verify your GitHub token works:

curl -H "Authorization: Bearer $GITHUB_TOKEN" \
  https://api.github.com/user
CursorGemini Code Assist