gemini-cli-rs

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Gemini CLI written in Rust, optimized for use as an MCP tool in Claude Code.

Features

• MCP Server mode — Runs as a native MCP server (--mcp-server); integrates directly with Claude Code
• SSE Streaming — Streams responses from the Gemini API in real time
• Google Search Grounding — Always-on; sources are printed to stderr in CLI mode and included in the response in MCP mode
• GEMINI.md Context — Loads project-specific context from GEMINI.md (walks up to the nearest .git root)
• Single-shot mode — Designed for non-interactive, scriptable use

Prerequisites

• A Gemini API key (GEMINI_API_KEY) — get one at Google AI Studio

Installation

Download pre-built binary

Pre-built binaries are available for macOS and Linux on the Releases page.

# Apple Silicon macOS
curl -L https://github.com/heki1224/gemini-cli-rs/releases/latest/download/gemini-cli-rs-aarch64-apple-darwin.tar.xz | tar -xJ
mv gemini ~/.local/bin/gemini

# Intel macOS
curl -L https://github.com/heki1224/gemini-cli-rs/releases/latest/download/gemini-cli-rs-x86_64-apple-darwin.tar.xz | tar -xJ
mv gemini ~/.local/bin/gemini

# Linux x86_64
curl -L https://github.com/heki1224/gemini-cli-rs/releases/latest/download/gemini-cli-rs-x86_64-unknown-linux-gnu.tar.xz | tar -xJ
mv gemini ~/.local/bin/gemini

Build from source

git clone https://github.com/heki1224/gemini-cli-rs
cd gemini-cli-rs
cargo build --release
cp target/release/gemini ~/.local/bin/gemini

Usage

CLI mode

# Set your API key
export GEMINI_API_KEY="your-api-key"

# Send a prompt
gemini -p "What is the capital of France?"

# Use a different model
gemini -m gemini-2.5-pro -p "Explain Rust's borrow checker"

Grounding sources are printed to stderr after the response.

MCP server mode

In MCP mode the binary is launched automatically by Claude Code — you do not normally run it directly. See MCP Setup for registration steps.

# Manual launch (for debugging)
GEMINI_API_KEY="your-api-key" gemini --mcp-server

Grounding sources are included in the response text (not stderr).

Options

Flag	Description	Default
-p, --prompt	Prompt to send (required in CLI mode)	—
-m, --model	Model to use	gemini-3-flash-preview
--mcp-server	Run as MCP server (JSON-RPC 2.0 over stdio)	—

The API key is read from the GEMINI_API_KEY environment variable only (no --api-key flag).

MCP Setup (Claude Code)

This tool is designed to be used as an MCP server inside Claude Code, providing Gemini with Google Search Grounding as a secondary AI assistant.

1. Build the binary

cargo build --release

2. Register as an MCP server

claude mcp add gemini /path/to/target/release/gemini --scope user -- --mcp-server

Use --scope user to make it available across all projects, or --scope project to limit it to the current project.

3. Set your API key

Add GEMINI_API_KEY to your shell profile (~/.zshrc, ~/.bashrc, etc.):

export GEMINI_API_KEY="your-api-key"

4. Restart Claude Code and verify

claude mcp list

Once registered, the ask_gemini_mcp tool is available. Claude Code routes prompts to Gemini with real-time Google Search grounding.

Note: The binary writes protocol messages to stdout and all logs to stderr. Do not redirect stderr if you want to see debug output.

GEMINI.md

Place a GEMINI.md file in your current working directory (or any parent directory) to inject system-level context into every request. The search walks up to the nearest .git directory; if no .git is found, it continues to the filesystem root. Useful for project-specific instructions.

Note: Files larger than 1 MB are silently ignored.

your-project/
├── .git/
├── GEMINI.md   ← loaded automatically
└── src/

License

MIT — see LICENSE