gemini-cli-mcp

A minimal MCP server that exposes Gemini CLI as a single tool callable from Claude Code (or any MCP client).

How it works

Claude Code sends prompts to this server via MCP. The server spawns gemini -p "..." in headless mode and returns the response. Gemini inherits your Google OAuth session — no API key required.

Claude Code ──MCP/stdio──▶ gemini-cli-mcp ──spawn──▶ gemini -p "..." --output-format json

Prerequisites

• Gemini CLI installed and authenticated:

  npm install -g @google/gemini-cli
  gemini  # complete the OAuth login flow

Installation

From source

git clone https://github.com/danwahl/gemini-cli-mcp
cd gemini-cli-mcp
npm install
npm run build

Configuration

User install (available across all projects):

claude mcp add gemini-cli -s user -- npx -y @danwahl/gemini-cli-mcp

Project install (shared with your team via .mcp.json):

claude mcp add gemini-cli -s project -- npx -y @danwahl/gemini-cli-mcp

Or from source, replace npx -y @danwahl/gemini-cli-mcp with node /absolute/path/to/gemini-cli-mcp/dist/index.js.

Verify with claude mcp list.

Tool: cli

| Parameter | Type | Required | Description | |-------------|--------|----------|-------------| | prompt | string | yes | Task or question to send to Gemini | | cwd | string | yes | Absolute path to working directory | | model | string | no | Model name or alias (see below). Omit to use Gemini CLI's default (auto). | | sessionId | string | no | Resume a previous session. The session ID is returned in the structured output of each call. |

Structured output

Each call returns structured content alongside the text response:

{
  "sessionId": "e80096bd-...",
  "response": "Gemini's answer...",
  "models": {
    "gemini-2.5-flash-lite": 1399,
    "gemini-3-flash-preview": 18635
  },
  "tools": {
    "list_directory": 2
  }
}

models maps model name → total tokens used. tools maps tool name → call count (only present when Gemini used tools).

Model aliases

These are passed directly to the CLI, which resolves them:

| Alias | Description | |--------------|-------------| | auto | Default routing (pro or preview depending on settings) | | pro | Complex reasoning tasks | | flash | Fast, balanced — good for most tasks | | flash-lite | Fastest, for simple tasks |

Or pass any concrete model name like "gemini-2.5-pro".

What Gemini can do

Gemini runs with --approval-mode yolo, giving it full tool access: read/write files, run shell commands, web search, and more. It operates in the cwd you specify.

Development

npm run build   # compile with tsc
npm test        # run unit tests

Smoke test

echo '{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{}}' | node dist/index.js

Design

One tool, no prompt wrappers. Claude Code is the orchestrator — it decides what to ask Gemini and how to phrase it. This server is a thin, reliable pipe between MCP and gemini -p.

See CLAUDE.md for project conventions.