GitHub Code Reviewer

An MCP (Model Context Protocol) server that gives Claude the ability to fetch Pull Request diffs from GitHub and post inline code review comments directly on the PR — either as a pending draft for you to approve, or published immediately.

How it works

You (Claude Code) ──► MCP Server (src/index.ts) ──► GitHub API
                           │
                     Two tools + two prompts exposed:
                     • get_pull_request_diff
                     • post_pr_review_comment
                     • review_pr (prompt — guided)
                     • review_pr_auto (prompt — autonomous)

When running as an MCP server, Claude can call these tools in response to natural language prompts. You describe which PR to review, and Claude fetches the diff, analyzes the code, and posts structured inline comments.

You can also use the built-in review_pr prompt to give Claude step-by-step instructions automatically — no need to describe the process manually each time.

Prompts available

There are two prompts, each with a different review style:

review_pr — guided review

Instructs Claude to follow a fixed step-by-step process: fetch the diff, analyze it across specific categories, and post inline comments.

Parameter	Type	Required	Description
owner	string	yes	GitHub username or organization
repo	string	yes	Repository name
pull_number	number	yes	PR number
status	string	no	PENDING (default) or PUBLIC

The prompt instructs Claude to focus on:

• Bugs and logic errors
• Security vulnerabilities
• Performance issues
• Code style and readability
• Missing error handling

review_pr_auto — autonomous review

Just fetches the diff and lets the LLM review freely using its own judgment — no rigid checklist.

Parameter	Type	Required	Description
owner	string	yes	GitHub username or organization
repo	string	yes	Repository name
pull_number	number	yes	PR number
status	string	no	PENDING (default) or PUBLIC

Tools available

get_pull_request_diff

Fetches the raw diff of a Pull Request from GitHub.

Parameter	Type	Description
owner	string	GitHub username or organization
repo	string	Repository name
pull_number	number	PR number

post_pr_review_comment

Posts an inline review comment on a specific line of a changed file.

Parameter	Type	Description
owner	string	GitHub username or organization
repo	string	Repository name
pull_number	number	PR number
path	string	File path (e.g. src/app.js)
line	number	Line number where the comment will appear
body	string	Comment text in Markdown
status	string	PENDING saves as a draft (you publish on GitHub); PUBLIC submits immediately

Prerequisites

• Node.js 18+
• A GitHub Personal Access Token with repo scope
• Claude Code (to use as an MCP server)

Installation

npm install

Configuration

Create a .env file in the project root:

GITHUB_TOKEN=ghp_YourGitHubTokenHere

Running as an MCP server (Claude Code)

Add this server to your Claude Code MCP configuration (~/.claude/claude_desktop_config.json or via claude mcp add):

{
  "mcpServers": {
    "github-code-reviewer": {
      "command": "npx",
      "args": ["tsx", "/path/to/mcp-github-reviewer/src/index.ts"],
      "env": {
        "GITHUB_TOKEN": "ghp_YourGitHubTokenHere"
      }
    }
  }
}

Or start the server manually:

npx -y @modelcontextprotocol/inspector@latest --mode cli npx tsx src/index.ts

Example usage

---

Guided review (step-by-step):

Use the prompt review_pr with owner="seu-usuario", repo="seu-repo", pull_number=42

---

Autonomous review (LLM decides):

Use the prompt review_pr_auto with owner="seu-usuario", repo="seu-repo", pull_number=42

---

Publish comments immediately:

Use the prompt review_pr with owner="seu-usuario", repo="seu-repo", pull_number=42, status="PUBLIC"

---

Manual prompt (without using any built-in prompt):

Review the PR 360 in seu-usuario/seu-repositorio and use post_pr_review_comment with status: "PENDING" so I can double-check everything on GitHub before publishing.

---

Project structure

mcp-github-reviewer/
├── src/
│   └── index.ts      # MCP server — exposes tools to Claude
├── package.json
├── tsconfig.json
└── .env              # GITHUB_TOKEN goes here

Dependencies

Package	Role
@modelcontextprotocol/sdk	MCP server framework
@octokit/rest	GitHub API client
dotenv	Loads .env variables
tsx	Runs TypeScript directly without a build step