README - godoc-mcp by captjt

godoc-mcp

[!IMPORTANT]
This is still in development. There are still some outstanding features/issues that need to be completed, use at your own risk.

A Model Context Protocol (MCP) server that provides real-time access to Go package documentation from pkg.go.dev, ensuring LLMs always have the latest and most accurate Go ecosystem information.

Features

🚀 Real-time Documentation: Fetches the latest documentation directly from pkg.go.dev
📦 Comprehensive Coverage: Access any public Go package documentation
🔍 Smart Search: Search for packages by name or functionality
📌 Version Support: Query specific versions or get the latest stable version
📊 Module Index Integration: Uses official Go module index for version discovery
⚡ Performance Optimized: Intelligent caching for fast responses
🛡️ Reliable: Graceful handling of network issues with fallback to cached data
🔧 Easy Integration: Works with any MCP-compatible LLM client

Why godoc-mcp?

Large Language Models often have outdated knowledge about Go packages and their APIs. The Go ecosystem moves fast, with popular packages receiving frequent updates. This MCP server bridges that gap by providing:

Current function signatures and documentation
Up-to-date type definitions and methods
Latest best practices and examples
Real-time access to new packages as they're published

Installation

# Clone the repository
git clone https://github.com/captjt/godoc-mcp.git
cd godoc-mcp

# Install dependencies
npm install

# Build the server
npm run build

Quick Start

Build the project:
```
npm run build
```

Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "godoc": {
      "command": "node",
      "args": ["/absolute/path/to/godoc-mcp/dist/index.js"]
    }
  }
}

Restart Claude Desktop
Test it by asking Claude about Go packages:
- "Show me the documentation for the fmt package"
- "What functions are available in the strings package?"
- "Search for Go web frameworks"

Usage

Starting the Server

# Run in production mode
npm start

# Run in development mode (with auto-reload)
npm run dev

# Run with debug logging
LOG_LEVEL=debug npm start

Configuration

Configure the server using environment variables:

# Server configuration
export GODOC_MCP_PORT=8080
export GODOC_MCP_HOST=localhost

# Cache configuration
export GODOC_MCP_CACHE_TTL=3600  # Cache TTL in seconds
export GODOC_MCP_CACHE_SIZE=1000  # Max number of cached packages

# Performance tuning
export GODOC_MCP_MAX_CONCURRENT_REQUESTS=10
export GODOC_MCP_REQUEST_TIMEOUT=30

MCP Client Configuration

For Claude Desktop, add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "godoc": {
      "command": "node",
      "args": ["/absolute/path/to/godoc-mcp/dist/index.js"],
      "env": {
        "LOG_LEVEL": "info"
      }
    }
  }
}

Or if you've installed globally:

{
  "mcpServers": {
    "godoc": {
      "command": "godoc-mcp"
    }
  }
}

Available Tools

`get_package_doc`

Retrieves comprehensive documentation for a Go package, with optional version support.

// Example usage
get_package_doc({ package: 'fmt' });
get_package_doc({ package: 'github.com/gin-gonic/gin' });
get_package_doc({ package: 'github.com/gin-gonic/gin', version: 'v1.9.0' });
get_package_doc({ package: 'github.com/gin-gonic/gin', version: 'latest' });

`get_function_doc`

Gets detailed documentation for a specific function, with optional version support.

// Example usage
get_function_doc({ package: 'fmt', function: 'Printf' });
get_function_doc({ package: 'strings', function: 'Split' });
get_function_doc({ package: 'strings', function: 'Split', version: 'latest' });

`get_type_doc`

Retrieves documentation for types and their methods, with optional version support.

// Example usage
get_type_doc({ package: 'io', type: 'Reader' });
get_type_doc({ package: 'net/http', type: 'Client' });
get_type_doc({ package: 'net/http', type: 'Client', version: 'v1.21.0' });

`search_packages`

Searches for Go packages by name or description.

// Example usage
search_packages({ query: 'web framework' });
search_packages({ query: 'json parsing' });

`get_package_examples`

Retrieves example code for a package, with optional version support.

// Example usage
get_package_examples({ package: 'context' });
get_package_examples({ package: 'sync' });
get_package_examples({ package: 'sync', version: 'latest' });

`get_package_versions`

Lists all available versions of a Go package from the official module index.

// Example usage
get_package_versions({ package: 'github.com/gin-gonic/gin' });
get_package_versions({ package: 'golang.org/x/text' });

Example Interactions

Getting Started with a Package

User: "How do I use the new slog package for structured logging?"
Assistant: Let me fetch the latest documentation for the slog package...
[Uses get_package_doc and get_package_examples to provide current information]

Understanding Function Signatures

User: "What's the signature for http.HandleFunc?"
Assistant: I'll get the current documentation for that function...
[Uses get_function_doc to show the exact, current signature]

Exploring Package Capabilities

User: "What methods does io.Reader have?"
Assistant: Let me look up the io.Reader interface and its methods...
[Uses get_type_doc to list all current methods]

Working with Versions

User: "What versions of gin are available?"
Assistant: I'll check the available versions of the Gin web framework...
[Uses get_package_versions to list all versions with timestamps]

Version-Specific Documentation

User: "Show me the Router type from gin v1.8.0"
Assistant: I'll get the documentation for the Router type from Gin v1.8.0...
[Uses get_type_doc with version parameter]

Development

Project Structure

godoc-mcp/
├── src/
│   ├── index.ts             # MCP server entry point
│   ├── fetcher/
│   │   └── index.ts         # pkg.go.dev fetcher with HTML parsing
│   ├── cache/
│   │   └── index.ts         # In-memory caching implementation
│   ├── types/
│   │   └── index.ts         # TypeScript type definitions
│   └── utils/
│       └── logger.ts        # Winston logger configuration
├── dist/                    # Compiled JavaScript output
├── package.json
├── tsconfig.json
├── README.md
├── DESIGN.md
└── example-config.json      # Example MCP configuration

Running Tests

The project includes comprehensive integration tests that verify the fetching and caching behavior:

# Run core tests only (RECOMMENDED - no network calls)
npm run test:core

# Run all tests (will likely fail due to rate limiting)
npm test

# Run unit tests only
npm run test:unit

# Run tests in watch mode
npm run test:watch

# Run tests with coverage report
npm run test:coverage

⚠️ Important: pkg.go.dev aggressively rate limits requests, causing most integration tests to fail. This is expected and does not indicate a problem with the MCP server. Use npm run test:core to run tests that don't require network access.

Test Structure

Integration Tests (tests/integration/): Test real interactions with pkg.go.dev and caching behavior
- fetcher.test.ts: Tests fetching documentation from pkg.go.dev
- cache.test.ts: Tests caching performance and behavior
- module-index.test.ts: Tests Go module index integration
- end-to-end.test.ts: Tests complete user workflows
Unit Tests (tests/unit/): Test individual components in isolation
- cache.test.ts: Tests cache operations without external dependencies

Key Test Scenarios

Package Fetching: Verifies correct parsing of pkg.go.dev HTML
Caching Performance: Demonstrates 100x+ speed improvement with caching
Version Support: Tests fetching specific package versions
Error Handling: Ensures graceful degradation when pkg.go.dev is unavailable
Concurrent Access: Verifies thread-safe cache operations

Note: Integration tests may occasionally fail due to rate limiting or HTML structure changes on pkg.go.dev. See for troubleshooting guide.

Development Workflow

# Build the project
npm run build

# Run in development mode
npm run dev

# Clean build artifacts
npm run clean

# Code quality checks
npm run typecheck    # Type checking
npm run lint         # ESLint
npm run lint:fix     # Auto-fix linting issues
npm run format       # Format with Prettier
npm run format:check # Check formatting
npm run check        # Run all checks

Code Quality

The project uses several tools to maintain code quality:

TypeScript: Strict type checking enabled
ESLint: Enforces code quality and consistency
Prettier: Automatic code formatting
Husky: Pre-commit hooks to ensure quality
lint-staged: Only lint/format changed files

See for detailed guidelines.

Contributing

Fork the repository
Create your feature branch (git checkout -b feature/amazing-feature)
Commit your changes (git commit -m 'Add amazing feature')
Push to the branch (git push origin feature/amazing-feature)
Open a Pull Request

captjt/godoc-mcp