FastMCP PR Review

A GitHub PR review server built with FastMCP, with two review modes: fast and thorough.

Each mode is self-contained — read either file top-to-bottom to understand the complete pattern.

Review Modes

Tool	File	What it does
review_pr_fast	fast.py	One LLM call, structured output, no tools
review_pr_thorough	thorough.py	Multi-pass pipeline: filter → review → verify

Fast

One ctx.sample() call with result_type=PRReviewResult. Sends the full diff, gets back a structured review. Best for small PRs or quick checks.

Thorough

Multi-pass pipeline with batched file filtering, per-file review with a verification protocol, and agentic verification where the LLM explores the repo to confirm or disprove findings. Configurable intensity (conservative/balanced/aggressive). Only confirmed findings survive.

Quick Start

uv sync
cp .env.example .env
# edit .env with your GitHub and Gemini credentials

uv run fastmcp-pr-review
# or override runtime settings explicitly
uv run fastmcp-pr-review --gemini-model gemini-2.5-pro
make server-stdio
make server-http HOST=0.0.0.0 PORT=8000

The server auto-loads .env when started from the repo directory, and the Click launcher also reads GITHUB_TOKEN and GEMINI_API_KEY directly from the process environment. That means hosted environments like Horizon can inject those vars without extra CLI flags.

The server also exposes data tools: get_pr_info, get_pr_diff, get_pr_files.

Deploy to Horizon

For Horizon-style deployments that import a module and look for an mcp object, point it at the repo-root run_horizon_server.py. That file loads env vars and exposes:

mcp = create_server()

Set GITHUB_TOKEN and GEMINI_API_KEY in Horizon, and it can import run_horizon_server.py directly.

Add to Claude

Add the server to your Claude MCP config with a stdio entry that runs this repo through uv:

{
  "mcpServers": {
    "fastmcp-pr-review": {
      "type": "stdio",
      "command": "uv",
      "args": [
        "--directory",
        "/absolute/path/to/fastmcp-pr-review",
        "run",
        "fastmcp-pr-review",
        "--gemini-model",
        "gemini-2.5-pro"
      ],
      "env": {}
    }
  }
}

Keep GITHUB_TOKEN and GEMINI_API_KEY in /absolute/path/to/fastmcp-pr-review/.env or inject them via the host environment so Claude does not need inline secrets in its MCP config. Use CLI flags for non-secret runtime settings like the fallback Gemini model.

Makefile

The repo includes a Makefile for the common local workflows:

make server-stdio
make server-http HOST=0.0.0.0 PORT=8000
make format
make lint
make lint-fix
make typecheck
make test
make build

Development

See DEVELOPING.md for testing and sampling patterns, and docs/ARCHITECTURE.md for architecture and design decisions.

License

MIT