# MCP Go SDK [](https://codespaces.new/modelcontextprotocol/go-sdk) [](https://pkg.go.dev/github.com/modelcontextprotocol/go-sdk) [](https://scorecard.dev/viewer/?uri=github.com/modelcontextprotocol/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`](https://pkg.go.dev/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`](https://pkg.go.dev/github.com/modelcontextprotocol/go-sdk/jsonrpc) package is for users implementing their own transports. - The [`github.com/modelcontextprotocol/go-sdk/auth`](https://pkg.go.dev/github.com/modelcontextprotocol/go-sdk/auth) package provides some primitives for supporting OAuth. - The [`github.com/modelcontextprotocol/go-sdk/oauthex`](https://pkg.go.dev/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/`](/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: | SDK Version | Latest MCP Spec | All Supported MCP Specs | |-----------------|-------------------|----------------------------------------------------| | v1.4.0+ | 2025-11-25\* | 2025-11-25\*, 2025-06-18, 2025-03-26, 2024-11-05 | | v1.2.0 - v1.3.1 | 2025-11-25\*\* | 2025-11-25\*\*, 2025-06-18, 2025-03-26, 2024-11-05 | | v1.0.0 - v1.1.0 | 2025-06-18 | 2025-06-18, 2025-03-26, 2024-11-05 | \* 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: ```go 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: ```go 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/`](/examples/) directory contains more example clients and servers. ## Contributing We welcome contributions to the SDK! Please see [CONTRIBUTING.md](/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](https://github.com/mark3labs/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](https://github.com/metoro-io/mcp-golang) and [go-mcp](https://github.com/ThinkInAIXYZ/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](./LICENSE) file for details.