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.

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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

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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

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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.)

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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

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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).

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License

ISC