Code Review MCP Server

An MCP server designed to act as a Read-Only Intelligence Provider for code reviews. It connects LLMs (like Claude Desktop or Gemini) to your Git hosting platforms (GitLab & GitHub) to analyze Merge/Pull Requests, understand project context, and provide expert feedback.

Features

• Platform Agnostic: Supports both GitLab and GitHub.
• List PRs/MRs: See what needs review.
• Get Details: Understand the description, author, and intent.
• Get Diff: Retrieve and analyze code changes.
• Read Files: Fetch specific files from repositories at any ref (commit, branch, tag).
• Custom Guidelines: Configure your own code review guidelines.

Installation & Setup

You can use this MCP server in two ways:

Option A: Global Installation (Recommended)

Install the package globally via npm:

npm install -g mcp-server-code-review

Option B: Clone & Build (For Development)

Clone the repository and build it locally:

git clone <your-repo-url> mcp-server-code-review
cd mcp-server-code-review
npm install
npm run build

Configuration

The server requires environment variables for authentication. You should add these to your MCP Client configuration (e.g., Claude Desktop).

Environment Variables

| Variable | Description | Required For | | ------------------------------ | -------------------------------------------------------- | ----------------------- | | GITLAB_TOKEN | Your GitLab Personal Access Token. | GitLab | | GITLAB_URL | GitLab instance URL (default: https://gitlab.com). | GitLab (Self-Managed) | | GITHUB_TOKEN | Your GitHub Personal Access Token. | GitHub | | CODE_REVIEW_GUIDELINES_FILE | Path to a file containing custom code review guidelines. | Optional (Custom Rules) | | CODE_REVIEW_GUIDELINES | Inline custom code review guidelines text. | Optional (Custom Rules) |

Note: At least one of GITLAB_TOKEN or GITHUB_TOKEN must be provided. If CODE_REVIEW_GUIDELINES_FILE is set, it takes precedence over CODE_REVIEW_GUIDELINES.

MCP Server Configuration

Using Global Installation

{
  "mcpServers": {
    "code-review": {
      "command": "mcp-server-code-review",
      "env": {
        "GITLAB_TOKEN": "your_token_here",
        "GITHUB_TOKEN": "your_token_here"
      }
    }
  }
}

Using Local Clone

Replace /absolute/path/to/... with the actual full path to the project directory.

{
  "mcpServers": {
    "code-review": {
      "command": "node",
      "args": ["/absolute/path/to/mcp-server-code-review/dist/index.js"],
      "env": {
        "GITLAB_TOKEN": "your_token_here",
        "GITHUB_TOKEN": "your_token_here"
      }
    }
  }
}

With Self-Managed GitLab

{
  "mcpServers": {
    "code-review": {
      "command": "mcp-server-code-review",
      "env": {
        "GITLAB_TOKEN": "your_token_here",
        "GITLAB_URL": "https://gitlab.yourcompany.com"
      }
    }
  }
}

With Custom Code Review Guidelines

You can provide custom guidelines either as a file path or inline text:

{
  "mcpServers": {
    "code-review": {
      "command": "mcp-server-code-review",
      "env": {
        "GITHUB_TOKEN": "your_token_here",
        "GITLAB_TOKEN": "your_token_here",
        "GITLAB_URL": "https://gitlab.yourcompany.com",
        "CODE_REVIEW_GUIDELINES_FILE": "/path/to/your/guidelines.md"
      }
    }
  }
}

Or use inline guidelines:

{
  "mcpServers": {
    "code-review": {
      "command": "mcp-server-code-review",
      "env": {
        "GITHUB_TOKEN": "your_token_here",
        "CODE_REVIEW_GUIDELINES": "Focus on performance and security. Ensure all functions have proper error handling."
      }
    }
  }
}

Claude Desktop Configuration

Add the following to your claude_desktop_config.json file.

Path locations:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json
• Linux: ~/.config/Claude/claude_desktop_config.json

Claude Code (CLI) Configuration

Add the following to your settings.json file for global configuration, or .claude/settings.local.json in your project directory for project-specific configuration.

Path locations (global):

• macOS: ~/.claude/settings.json
• Windows: %USERPROFILE%\.claude\settings.json
• Linux: ~/.claude/settings.json

Gemini Configuration

Add the following to your settings.json file.

Path locations:

• macOS: ~/.gemini/settings.json
• Windows: %USERPROFILE%\.gemini\settings.json
• Linux: ~/.gemini/settings.json

ChatGPT Configuration

Add the following to your mcp.json file.

Path locations:

• macOS: ~/.chatgpt/mcp.json
• Windows: %USERPROFILE%\.chatgpt\mcp.json
• Linux: ~/.chatgpt/mcp.json

Available Tools

GitHub Tools

| Tool | Description | | --------------------------- | ------------------------------------------------- | | github_list_prs | List pull requests with optional status filter | | github_get_pr_details | Get detailed information about a pull request | | github_get_pr_diff | Retrieve code changes/diff for a pull request | | github_read_file | Read file content at a specific ref | | github_get_project_metadata | Fetch README and manifest files (package.json, etc.) |

GitLab Tools

| Tool | Description | | --------------------------- | ------------------------------------------------- | | gitlab_list_mrs | List merge requests with optional status filter | | gitlab_get_mr_details | Get detailed information about a merge request | | gitlab_get_mr_diff | Retrieve code changes/diff for a merge request | | gitlab_read_file | Read file content at a specific ref | | gitlab_get_project_metadata | Fetch README and manifest files (package.json, etc.) |

Available Prompts

| Prompt | Description | | ----------------------- | ------------------------------------------------ | | review_merge_request | Guided GitLab MR review with Principal Engineer perspective | | review_pull_request | Guided GitHub PR review with Principal Engineer perspective |

These prompts instruct the LLM to:

• Act as a Principal Software Engineer
• Focus on logic errors, race conditions, security issues, and architectural alignment
• Provide structured feedback (Summary, Critical Issues, Suggestions, Nitpicks)
• Request issue/ticket details for additional context

Development & Debugging

Run Unit Tests

npm test              # Run all tests
npm run test:coverage # Run tests with coverage report

Format Code

npm run format        # Format code with Prettier
npm run format:check  # Check code formatting

Test with MCP Inspector

The MCP Inspector allows you to test the server and tool calls interactively in your browser without needing the Claude Desktop app.

1. Build the project:

   npm run build

2. Run the Inspector: (Replace tokens with your actual values)

   GITLAB_TOKEN=your_token npx @modelcontextprotocol/inspector node dist/index.js

3. Open: http://localhost:6274 (or the port shown in terminal).

License

ISC