mcp-go
A Go implementation of the Model Context Protocol (MCP), enabling seamless integration between LLM applications and external data sources and tools.
A Go library for building MCP servers, programs that let AI assistants like Claude call custom tools, read data sources, and use prompt templates you define, with a working hello-world example in about 30 lines.
This library provides a way to build MCP servers in Go. MCP, or Model Context Protocol, is a standard that lets AI assistants (like Claude or similar chat tools) connect to external programs and data sources in a structured way. Instead of an AI only knowing what you type to it, MCP lets it call out to tools you define, read data from sources you expose, and use prompt templates you set up. This library is the Go language implementation of that protocol.
The core idea is that you write a small Go program that defines what tools and data your server offers. A tool might do something like perform a calculation, query a database, or look something up. The MCP library handles all the protocol-level communication between your program and whatever AI client is connecting to it. You define what the tool does and what inputs it accepts; the library handles the rest. The README opens with a working example that creates a hello-world tool in about 30 lines of code.
Servers built with this library can expose three kinds of things: resources (read-only data the AI can load, similar to a web page you fetch), tools (actions the AI can trigger, similar to a form submission), and prompts (reusable templates for structuring AI interactions). The library supports two transport modes for connecting clients to servers: standard input/output for simple integrations, and HTTP with Server-Sent Events for web-based setups.
More advanced features documented in the README include session management (so different connected clients can have different tool sets), request hooks (code that runs before or after each request), and middleware for tool handlers. The library targets the MCP specification version 2025-11-25 and is backward compatible with several earlier versions.
The project is written in Go and installed with a single go get command. It is under active development, and the README notes that while core features work, some advanced capabilities are still being built. The full README is longer than what was shown.
Where it fits
- Build an MCP server in Go that exposes a database query tool so an AI assistant can look up live information from your database.
- Create custom action tools that an AI assistant can trigger to interact with your internal systems or external APIs.
- Expose read-only data resources so an AI client can fetch and use content from your application.
- Set up reusable prompt templates that structure how an AI handles specific types of requests to your server.