MCP-Go

MCP-Go

What is MCP?

MCP (Model Context Protocol) is a lightweight, flexible protocol designed for efficient communication between AI models and applications. It provides a standardized way for services to exchange messages, tools, and resources while maintaining high performance and reliability.

About this Package

MCP-Go is a Go implementation of the Model Context Protocol that provides a robust framework for AI communication:

• Client-Server Architecture: Complete implementation of both client and server components
• Transport Flexibility: Seamlessly communicate via Standard I/O, WebSockets, or HTTP
• Concurrent Design: Built from the ground up with Go's goroutines and channels
• Type-Safe APIs: Strong typing throughout the codebase to prevent runtime errors
• Modular Components: Handler-based design pattern for extensibility and maintainability
• Session Management: Persistent connections with proper lifecycle handling

Usage

Common Pattern

All MCP-Go implementations follow a similar pattern:

package main

import (
    "github.com/OkutaniDaichi0106/mcp-go/mcp"
)

func main() {
    server := mcp.NewServer()

    // Tool registration
    mcp.HandleToolFunc(&mcp.ToolDefinition{
        Name:        "tool_name",
        Description: "Tool description",
        InputSchema: mcp.InputSchema(`{ "type": "object", ... }`),
    }, func(w mcp.ContentsWriter, name string, args map[string]any) {
        // Tool implementation
        // ...
        w.WriteContents(contents)
    })

    // Resource registration
    mcp.HandleResourceFunc(&mcp.ResourceDefinition{
        URI:         "resource_uri",
        MimeType:    "resource_mime_type",
        Name:        "resource_name",
        Description: "Resource description",
    }, func(w mcp.ContentsWriter, uri string) {
        // Resource implementation
        // ...
        w.WriteContents(contents)
    })

    // Prompt registration
    mcp.HandlePromptFunc(&mcp.PromptDefinition{
        Name:        "prompt_name",
        Description: "Prompt description",
        InputSchema: mcp.InputSchema(`{ "type": "object", ... }`),
    }, func(w mcp.PromptWriter, name string, args map[string]any) {
        // Prompt implementation
        // ...
        w.WriteContents(contents)
    })

    transport, err := ... // Create transport

    // Configure transport and accept -> get session
    session, err := server.Accept(transport)
    defer session.Close()

    // ...
}

package main

import (
    "github.com/OkutaniDaichi0106/mcp-go/mcp"
)

func main() {
    // Sample registration
    mcp.HandleSampleFunc(&mcp.SampleDefinition{
        Name:        "sample_name",
        Description: "Sample description",
    }, func(w mcp.ContentsWriter, name string, args map[string]any) {
        // Sample implementation
        // ...
        w.WriteContents(contents)
    })

    // Root registration
    mcp.HandleRoot(&mcp.RootDefinition{
        URI:  "root_uri",
        Name: "Root name",
    })

    // Create client
    client := mcp.NewClient()

    transport, err := ... // Create transport

    // Configure transport and dial -> get session
    session, err := client.Dial(transport)
    defer session.Close()

    // ...
}

Transport Options

MCP-Go supports multiple transport methods with minimal code changes:

Custom Transports

For custom transports, use the Accept and Dial methods with the appropriate transport object.

// Server
sess, err := server.Accept(t)

// Client
sess, err := client.Dial(t)

Standard I/O

For Standard I/O, use the AcceptStdio and DialStdio methods.

// Server
sess, err := server.AcceptStdio()

// Client
sess, err := client.DialStdio("command", "arg1", "arg2")

HTTP

With HTTP, you can use the AcceptHTTP and DialHTTP methods.

// Server
http.HandleFunc("/mcp", func(w http.ResponseWriter, r *http.Request) {
    sess, err := server.AcceptHTTP(w, r)
})

// Client
sess, err := client.DialHTTP("http://localhost:8080/mcp", nil)

Specification Compliance

MCP-Go implements the Model Context Protocol specification v2025-03-26, which is the latest version of the protocol as of this release.

Installation

go get github.com/OkutaniDaichi0106/mcp-go

Documentation

For detailed API documentation and advanced usage examples, please refer to our GoDoc.

License

This project is licensed under the MIT License - see the LICENSE file for details.