Ask Codex MCP

MCP server that connects any AI client to OpenAI Codex CLI

An MCP server for AI-to-AI collaboration via the Codex CLI. Works with Claude Code, Claude Desktop, Cursor, Warp, Copilot, and 40+ other MCP clients. Access GPT-5.5 for code generation, analysis, and review with automatic fallback to GPT-5.5-mini on quota limits.

Part of the Ask LLM monorepo.

Quick Start

Claude Code

claude mcp add codex -- npx -y ask-codex-mcp

Claude Desktop

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "codex": {
      "command": "npx",
      "args": ["-y", "ask-codex-mcp"]
    }
  }
}

Any MCP Client

{
  "command": "npx",
  "args": ["-y", "ask-codex-mcp"]
}

Prerequisites

• Node.js v20.0.0 or higher
• Codex CLI installed and authenticated

Tools

| Tool | Purpose | |------|---------| | ask-codex | Send prompts to Codex CLI. Defaults to GPT-5.5 with automatic mini fallback | | ping | Connection test — verify MCP setup without using tokens |

Models

| Model | Use Case | |-------|----------| | gpt-5.5 | Default — highest capability | | gpt-5.5-mini | Automatic fallback on quota errors |

Environment variables

| Variable | Default | Purpose | |----------|---------|---------| | ASK_CODEX_MODEL | gpt-5.5 | Override the default model | | ASK_CODEX_FALLBACK_MODEL | gpt-5.5-mini | Override the quota-fallback model | | ASK_CODEX_LOAD_USER_CONFIG | (unset) | Set to 1 to opt back into loading ~/.codex/config.toml (hooks, MCP servers, preferences) and execpolicy .rules files. By default the wrapper passes --ignore-user-config --ignore-rules so behavior stays deterministic across host machines. Auth credentials in CODEX_HOME always load regardless. See ADR-071. | | GMCPT_TIMEOUT_MS | 210000 | Per-call timeout for the spawned codex process | | GMCPT_LOG_LEVEL | warn | debug, info, warn, or error |

Documentation

Full docs at lykhoyda.github.io/ask-llm

License

MIT