grok-mcp

Use Grok as a peer code reviewer and rigorous second-opinion consultant inside Claude Code, Cursor, Cline, OpenClaw, and any other MCP host — talking to xAI's API directly (just an XAI_API_KEY, no install) or via the official Grok CLI.

grok-mcp (npm: grok-cli-mcp) is a Model Context Protocol server for Grok. It gives your primary agent (Claude, Cursor, etc.) four tools so it can delegate to Grok for high-quality second opinions and rigorous validation without leaving the session. As of v0.3.0 it talks to xAI's API directly — no grok binary required — and still supports the CLI for OAuth users:

• grok_review — structured diff review with per-dimension scores
• grok_challenge — thorough analysis for bugs, races, edge cases and security issues
• grok_consult — multi-turn consultation (caller owns history)
• grok_chat — one-shot questions

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Why grok-mcp?

Most "Grok MCP" packages expose Grok's chat/search/image capabilities so Claude can use Grok. grok-mcp lets your main coding agent (Claude/Cursor/…) ask Grok for a rigorous second opinion on its own work. A different model providing thorough review often catches issues that single-model loops miss.

What you get

Four tools, all stateless, all stdout-only:

Tool	Use it for
grok_chat	One-shot prompt → Grok's reply
grok_review	Pass a unified diff (or auto-grab git diff main...HEAD) and get a per-dimension code review
grok_consult	Replay a message history for multi-turn — caller owns the thread
grok_challenge	Rigorous analysis: ask Grok to surface bugs, race conditions, edge cases, and security issues

Prerequisites

• Node.js ≥ 18
• A backend (the server picks one automatically — see Backends):
  • API mode (recommended, zero install): an XAI_API_KEY from console.x.ai. The server calls xAI's HTTP API directly — no extra binary needed.
  • CLI mode: the Grok CLI installed, used when no XAI_API_KEY is set:

    curl -fsSL https://x.ai/cli/install.sh | bash
    

    Then authenticate with browser OAuth (run grok once interactively). See Authentication below.

Install

npm install -g grok-cli-mcp
# or use npx — no install needed
npx grok-cli-mcp

Why the npm name is grok-cli-mcp instead of grok-mcp? The bare grok-mcp name on npm was already taken by an unrelated project (a Grok HTTP-API integration). The brand, GitHub repo, and MCP server identity stay grok-mcp; only the npm install identifier is grok-cli-mcp — chosen to highlight that this server wraps the official Grok CLI.

Authentication

There are two auth methods, each tied to a backend:

Method	Backend	Best for	Rate limits
API key (XAI_API_KEY env var)	API mode — no grok binary needed	MCP / CI / automation	Pay-per-call, no subscription cap
Browser OAuth (grok interactive login)	CLI mode	Local interactive use	Subject to your grok.com plan tier

Setting XAI_API_KEY switches the server to API mode, so you can keep your browser login for interactive grok use and use a key just for this MCP server via its env block:

{
  "mcpServers": {
    "grok": {
      "command": "npx",
      "args": ["-y", "grok-cli-mcp"],
      "env": {
        "XAI_API_KEY": "xai-...",
        "GROK_MCP_TIMEOUT": "600000"
      }
    }
  }
}

Treat the key file as a secret — it ends up in your MCP host's config (e.g. ~/.claude.json), which is plain JSON on disk.

Wire it into your MCP host

Claude Code

Recommended — use add-json so the env block parses cleanly:

claude mcp add-json -s user grok '{
  "command": "npx",
  "args": ["-y", "grok-cli-mcp"],
  "env": { "XAI_API_KEY": "xai-...", "GROK_MCP_TIMEOUT": "600000" }
}'

Why add-json not claude mcp add -e ...? The -e KEY=val flag is variadic and will greedily consume the server name as another env value if you pass more than one. add-json sidesteps that footgun entirely.

Or edit ~/.claude.json directly. Minimal (OAuth fallback):

{
  "mcpServers": {
    "grok": {
      "command": "npx",
      "args": ["-y", "grok-cli-mcp"]
    }
  }
}

Cursor

Create .cursor/mcp.json (project) or ~/.cursor/mcp.json (global):

{
  "mcpServers": {
    "grok": {
      "command": "npx",
      "args": ["-y", "grok-cli-mcp"]
    }
  }
}

Cline (VS Code)

Settings → Cline → MCP Servers:

{
  "grok": {
    "command": "npx",
    "args": ["-y", "grok-cli-mcp"]
  }
}

Any other MCP host

grok-mcp speaks plain stdio MCP. Point any client at npx -y grok-cli-mcp and it works.

Tool reference

grok_chat

{ "prompt": "Explain consistent hashing in two sentences." }

Optional: model to override the default Grok model; timeout (seconds) to extend the per-call limit for long grok-4 reasoning. All four tools accept timeout.

grok_review

{ "base_ref": "main", "focus": "security" }

If diff is omitted, runs git diff <base_ref>...HEAD in cwd (defaults to your host's working directory). Returns a markdown review by default with verdict, per-dimension scores (correctness / readability / architecture / security / performance), and concrete fix-it items.

Pass "format": "json" to get machine-parseable output suitable for CI gating — see Use as a PR gate.

grok_consult

{
  "messages": [
    { "role": "system", "content": "You are a senior backend engineer." },
    { "role": "user", "content": "How would you cache this query?" },
    { "role": "assistant", "content": "Two options..." },
    { "role": "user", "content": "What's the failure mode of option 2?" }
  ]
}

The server is stateless — the caller passes the full thread each time. Most MCP hosts handle this naturally.

grok_challenge

{
  "code": "function transfer(from, to, amount) { from.balance -= amount; to.balance += amount; }",
  "context": "Node.js, called concurrently from HTTP handlers"
}

Returns severity-ranked issues (Critical / High / Medium / Low) with concrete reproductions and patches.

Configuration

Env var	Default	Purpose
XAI_API_KEY	(unset — falls back to OAuth)	API key from console.x.ai. When set, the server uses API mode (direct HTTP) and bills pay-per-call with no subscription rate cap. See Authentication.
GROK_MCP_BACKEND	auto	Which backend to use: api (direct HTTP), cli (shell out to grok), or auto (API when XAI_API_KEY is set, else CLI). See Backends.
GROK_MCP_MODEL	grok-4	Model used in API mode. (CLI mode reads ~/.grok/config.toml.)
GROK_MCP_BASE_URL	https://api.x.ai/v1	API base URL — point at a proxy or compatible gateway in API mode.
GROK_MCP_BIN	grok	Path to the grok binary (CLI mode only)
GROK_MCP_TIMEOUT	300000	Default per-call timeout in milliseconds

Backends

The server can reach Grok two ways and chooses one at startup (it logs which to stderr):

• API mode — calls xAI's OpenAI-compatible /chat/completions endpoint directly using Node's built-in fetch. No grok binary required, cleaner errors, pay-per-call. Selected when XAI_API_KEY is set, or forced with GROK_MCP_BACKEND=api.
• CLI mode — shells out to the installed grok binary (supports browser OAuth). Selected when no XAI_API_KEY is set, or forced with GROK_MCP_BACKEND=cli.

Force a mode with GROK_MCP_BACKEND. In API mode, set the model with GROK_MCP_MODEL; in CLI mode, model defaults live in ~/.grok/config.toml.

Timeouts

grok-4 is a reasoning model and long prompts routinely take longer than two minutes. The server's default per-call limit is 300s (5 min). You can change it three ways:

• Per call — pass timeout (seconds) to any tool: { "prompt": "...", "timeout": 600 }.
• Per server — set GROK_MCP_TIMEOUT (milliseconds) in the MCP server's env.
• Host side — the MCP host has its own request timeout that can fire before the server's. If calls still time out after raising the above, raise the host limit too. In Claude Code that's MCP_TIMEOUT (server startup) and MCP_TOOL_TIMEOUT (per tool call), both in milliseconds.

On timeout the error includes any partial output Grok produced before the deadline, so you don't lose a near-complete answer.

Use as a PR gate (CI)

grok-mcp ships a grok-review-ci bin and a composite GitHub Action so Grok can review every PR and fail the check on block.

Drop this into .github/workflows/grok-review.yml in your repo:

name: Grok review
on: { pull_request: { branches: [main] } }
permissions: { contents: read, pull-requests: write }
jobs:
  grok:
    runs-on: ubuntu-latest
    if: ${{ github.event.pull_request.head.repo.full_name == github.repository }}
    steps:
      - uses: actions/checkout@v4
        with: { fetch-depth: 0 }
      - uses: howardpen9/grok-mcp/.github/actions/grok-review@main
        with:
          xai-api-key: ${{ secrets.XAI_API_KEY }}
          gate-on: block      # also accepts: block,request_changes
          # focus: security   # optional
          # min-score: 6      # optional — fail any dimension below this

The action posts a sticky PR comment with verdict + per-dimension scores + concrete blockers, and exits non-zero (failing the check) when the verdict matches gate-on. Full example with comments: examples/workflows/grok-review.yml.

Want JSON straight from the tool instead? Pass format: "json" to grok_review — same schema as the bin emits, suitable for any pipeline:

{
  "verdict": "block",
  "summary": "Unparameterised SQL query in src/db.ts.",
  "scores": { "correctness": 4, "readability": 7, "architecture": 5, "security": 2, "performance": 8 },
  "blockers": [
    { "severity": "critical", "title": "SQL injection", "file": "src/db.ts", "line": 42,
      "reason": "User input concatenated directly into the query.",
      "fix": "Use the parameterised form `db.query(sql, [userId])`." }
  ],
  "notes": []
}

Roadmap

• v0.1 — four stateless tools, stdio transport
• Discoverability push (v0.1.3, shipped) — naming unification, MCP Registry, Smithery, glama.ai, stronger positioning. See docs/improvement-plan.md and CHANGELOG.md.
• v0.2 (shipped) — grok_review JSON mode + grok-review-ci bin + GitHub Action for PR gating.
• v0.3 (current) — direct xAI API backend (no grok CLI required); GROK_MCP_BACKEND api/cli/auto.
• v0.4 — server-side session persistence so grok_consult can take a conversation_id
• v0.5 — streaming responses through MCP progress notifications

Development

git clone https://github.com/howardpen9/grok-mcp.git
cd grok-mcp
npm install
npm test
npm run build

Contact

Bug reports & feature requests → GitHub issues. DMs welcome on X: @0xHoward_Peng.

License

MIT