MCP Go SDK

This repository contains an implementation of the official Go software
development kit (SDK) for the Model Context Protocol (MCP).

Package / Feature documentation

The SDK consists of several importable packages:

• The
  github.com/modelcontextprotocol/go-sdk/mcp
  package defines the primary APIs for constructing and using MCP clients and
  servers.
• The
  github.com/modelcontextprotocol/go-sdk/jsonrpc package is for users implementing
  their own transports.
• The
  github.com/modelcontextprotocol/go-sdk/auth
  package provides some primitives for supporting OAuth.
• The
  github.com/modelcontextprotocol/go-sdk/oauthex
  package provides extensions to the OAuth protocol, such as ProtectedResourceMetadata.

The SDK endeavors to implement the full MCP spec. The docs/ directory
contains feature documentation, mapping the MCP spec to the packages above.

Version Compatibility

The following table shows which versions of the Go SDK support which versions of the MCP specification:

* Client side OAuth has experimental support.

** Partial support for 2025-11-25 (client side OAuth and Sampling with tools not available).

New releases of the SDK target only supported versions of Go. See
https://go.dev/doc/devel/release#policy for more information.

Getting started

To get started creating an MCP server, create an mcp.Server instance, add
features to it, and then run it over an mcp.Transport. For example, this
server adds a single simple tool, and then connects it to clients over
stdin/stdout:

package main

import (
	"context"
	"log"

	"github.com/modelcontextprotocol/go-sdk/mcp"
)

type Input struct {
	Name string `json:"name" jsonschema:"the name of the person to greet"`
}

type Output struct {
	Greeting string `json:"greeting" jsonschema:"the greeting to tell to the user"`
}

func SayHi(ctx context.Context, req *mcp.CallToolRequest, input Input) (
	*mcp.CallToolResult,
	Output,
	error,
) {
	return nil, Output{Greeting: "Hi " + input.Name}, nil
}

func main() {
	// Create a server with a single tool.
	server := mcp.NewServer(&mcp.Implementation{Name: "greeter", Version: "v1.0.0"}, nil)
	mcp.AddTool(server, &mcp.Tool{Name: "greet", Description: "say hi"}, SayHi)
	// Run the server over stdin/stdout, until the client disconnects.
	if err := server.Run(context.Background(), &mcp.StdioTransport{}); err != nil {
		log.Fatal(err)
	}
}

To communicate with that server, create an mcp.Client and connect it to the
corresponding server, by running the server command and communicating over its
stdin/stdout:

package main

import (
	"context"
	"log"
	"os/exec"

	"github.com/modelcontextprotocol/go-sdk/mcp"
)

func main() {
	ctx := context.Background()

	// Create a new client, with no features.
	client := mcp.NewClient(&mcp.Implementation{Name: "mcp-client", Version: "v1.0.0"}, nil)

	// Connect to a server over stdin/stdout.
	transport := &mcp.CommandTransport{Command: exec.Command("myserver")}
	session, err := client.Connect(ctx, transport, nil)
	if err != nil {
		log.Fatal(err)
	}
	defer session.Close()

	// Call a tool on the server.
	params := &mcp.CallToolParams{
		Name:      "greet",
		Arguments: map[string]any{"name": "you"},
	}
	res, err := session.CallTool(ctx, params)
	if err != nil {
		log.Fatalf("CallTool failed: %v", err)
	}
	if res.IsError {
		log.Fatal("tool failed")
	}
	for _, c := range res.Content {
		log.Print(c.(*mcp.TextContent).Text)
	}
}

The examples/ directory contains more example clients and
servers.

Contributing

We welcome contributions to the SDK! Please see
CONTRIBUTING.md for details of how to contribute.

Acknowledgements / Alternatives

Several third party Go MCP SDKs inspired the development and design of this
official SDK, and continue to be viable alternatives, notably
mcp-go, originally authored by Ed Zynda.
We are grateful to Ed as well as the other contributors to mcp-go, and to
authors and contributors of other SDKs such as
mcp-golang and
go-mcp. Thanks to their work, there
is a thriving ecosystem of Go MCP clients and servers.

License

This project is licensed under Apache 2.0 for new contributions, with existing
code under MIT - see the LICENSE file for details.