MCP GitLab Review

An MCP (Model Context Protocol) server for AI-powered GitLab merge request code reviews. It provides clean, structured, agent-friendly access to GitLab MR data — no raw diffs, no parsing headaches.

Features

• Structured diff parsing — converts raw unified diffs into clean JSON with line numbers, change types, and hunk boundaries
• File prioritization — automatically classifies changed files by review importance (high/medium/low/skip), filtering out generated code, vendor files, and lock files
• Lazy loading — tools designed for incremental exploration: start with overview, drill into specific files
• In-memory caching — aggressive caching of GitLab API responses with configurable TTL
• Clean architecture — modular Go design with fx dependency injection, separated by domain concerns

Tools

Tool	Description
get_mr_summary	MR metadata: title, description, author, branches, commit messages, status
get_changed_files	Prioritized list of all changed files with change type, priority, language, line counts
get_file_context	Full file content at source branch + structured parsed diff for a specific file
get_architecture_view	Repository folder/file tree at source branch, optionally filtered to subdirectory
post_review_comment	Post general or line-specific review comments on the MR

Architecture

cmd/server/              → Entry point
internal/
  app/                   → Application wiring (fx)
  module/
    gitlab/              → GitLab API client, caching service
      domain/            → Domain models, MR URL parser
      repository/        → HTTP client for GitLab REST API
      service/           → Business logic with caching layer
    diff/                → Diff parsing and file classification
      domain/            → Diff models (hunks, lines, priorities)
      service/           → Unified diff parser, file prioritizer
    mcp/                 → MCP server and tool handlers
      presentation/      → Tool definitions, request handlers
      service/           → Orchestration service
  platform/
    config/              → Configuration loading (YAML + env vars)
    logger/              → Zap logger with pretty console output
    cache/               → In-memory TTL cache
config/
  base.yaml              → Base configuration file

Prerequisites

• Go 1.21+
• GitLab personal access token with api scope

Setup

1. Clone the repository:

   git clone <repo-url>
   cd mcp-gitlab-review

2. Create a .env file from the example:

   cp .env.example .env

3. Edit .env and set your GitLab token:

   GITLAB_PERSONAL_ACCESS_TOKEN=glpat-xxxxxxxxxxxxxxxxxxxx
   GITLAB_API_URL=https://gitlab.com/api/v4
   

4. Build:

   go build -o mcp-gitlab-review ./cmd/server

Usage

As an MCP server (stdio transport)

The server communicates via stdin/stdout using the MCP protocol:

./mcp-gitlab-review

MCP Client Configuration

Add to your MCP client configuration (e.g., Claude Desktop, Cursor, etc.):

{
  "mcpServers": {
    "gitlab-review": {
      "command": "/path/to/mcp-gitlab-review",
      "env": {
        "GITLAB_PERSONAL_ACCESS_TOKEN": "glpat-xxxxxxxxxxxxxxxxxxxx",
        "GITLAB_API_URL": "https://gitlab.com/api/v4"
      }
    }
  }
}

Tool Examples

Get MR summary:

{
  "tool": "get_mr_summary",
  "arguments": {
    "mr_url": "https://gitlab.com/group/project/-/merge_requests/123"
  }
}

Get changed files (prioritized):

{
  "tool": "get_changed_files",
  "arguments": {
    "mr_url": "https://gitlab.com/group/project/-/merge_requests/123"
  }
}

Get file with structured diff:

{
  "tool": "get_file_context",
  "arguments": {
    "mr_url": "https://gitlab.com/group/project/-/merge_requests/123",
    "file_path": "internal/service/handler.go"
  }
}

Get architecture view:

{
  "tool": "get_architecture_view",
  "arguments": {
    "mr_url": "https://gitlab.com/group/project/-/merge_requests/123",
    "path": "internal"
  }
}

Post a review comment:

{
  "tool": "post_review_comment",
  "arguments": {
    "mr_url": "https://gitlab.com/group/project/-/merge_requests/123",
    "body": "This function needs error handling for the nil case.",
    "file_path": "internal/service/handler.go",
    "new_line": 42
  }
}

File Priority Classification

Changed files are automatically classified to help the AI agent focus on what matters:

Priority	Files
High	New files, business logic, deleted files
Medium	Test files
Low	Config files, migrations
Skip	Generated code (.pb.go, _gen.go), vendor/, lock files (go.sum, package-lock.json)

Configuration

Configuration is loaded from config/base.yaml with environment variable expansion:

gitlab:
  apiURL: "${GITLAB_API_URL:https://gitlab.com/api/v4}"
  token: "${GITLAB_PERSONAL_ACCESS_TOKEN}"

cache:
  ttl: 5m
  maxSize: 1000

mcp:
  name: "gitlab-review"
  version: "1.0.0"

Testing

go test ./... -v

Tech Stack

• mark3labs/mcp-go — MCP protocol implementation
• go.uber.org/fx — Dependency injection
• go.uber.org/zap — Structured logging
• go.uber.org/config — YAML configuration
• joho/godotenv — Environment variable loading
• thessem/zap-prettyconsole — Pretty console output
• stretchr/testify — Test assertions

License

MIT