6e03217c83Handlers and client/server methods take a single request argument combining the session and params. This slightly simplifies the signature for handlers, since there is no longer an often-ignored session argument. But more importantly, it opens the door to adding more information in requests, such as auth info and HTTP request headers. For #243.
151 lines
4.7 KiB
Markdown
151 lines
4.7 KiB
Markdown
<!-- Autogenerated by weave; DO NOT EDIT -->
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# MCP Go SDK v0.2.0
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[](https://codespaces.new/modelcontextprotocol/go-sdk)
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***BREAKING CHANGES***
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This version contains breaking changes.
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See the [release notes](
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https://github.com/modelcontextprotocol/go-sdk/releases/tag/v0.2.0) for details.
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[](https://pkg.go.dev/github.com/modelcontextprotocol/go-sdk)
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This repository contains an unreleased implementation of the official Go
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software development kit (SDK) for the Model Context Protocol (MCP).
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> [!WARNING]
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> The SDK should be considered unreleased, and is currently unstable
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> and subject to breaking changes. Please test it out and file bug reports or API
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> proposals, but don't use it in real projects. See the issue tracker for known
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> issues and missing features. We aim to release a stable version of the SDK in
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> August, 2025.
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## Design
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The design doc for this SDK is at [design.md](./design/design.md), which was
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initially reviewed at
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[modelcontextprotocol/discussions/364](https://github.com/orgs/modelcontextprotocol/discussions/364).
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Further design discussion should occur in
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[issues](https://github.com/modelcontextprotocol/go-sdk/issues) (for concrete
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proposals) or
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[discussions](https://github.com/modelcontextprotocol/go-sdk/discussions) for
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open-ended discussion. See [CONTRIBUTING.md](/CONTRIBUTING.md) for details.
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## Package documentation
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The SDK consists of three importable packages:
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- The
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[`github.com/modelcontextprotocol/go-sdk/mcp`](https://pkg.go.dev/github.com/modelcontextprotocol/go-sdk/mcp)
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package defines the primary APIs for constructing and using MCP clients and
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servers.
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- The
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[`github.com/modelcontextprotocol/go-sdk/jsonschema`](https://pkg.go.dev/github.com/modelcontextprotocol/go-sdk/jsonschema)
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package provides an implementation of [JSON
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Schema](https://json-schema.org/), used for MCP tool input and output schema.
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- The
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[`github.com/modelcontextprotocol/go-sdk/jsonrpc`](https://pkg.go.dev/github.com/modelcontextprotocol/go-sdk/jsonrpc) package is for users implementing
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their own transports.
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## Example
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In this example, an MCP client communicates with an MCP server running in a
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sidecar process:
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```go
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package main
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import (
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"context"
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"log"
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"os/exec"
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"github.com/modelcontextprotocol/go-sdk/mcp"
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)
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func main() {
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ctx := context.Background()
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// Create a new client, with no features.
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client := mcp.NewClient(&mcp.Implementation{Name: "mcp-client", Version: "v1.0.0"}, nil)
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// Connect to a server over stdin/stdout
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transport := &mcp.CommandTransport{Command: exec.Command("myserver")}
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session, err := client.Connect(ctx, transport, nil)
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if err != nil {
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log.Fatal(err)
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}
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defer session.Close()
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// Call a tool on the server.
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params := &mcp.CallToolParams{
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Name: "greet",
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Arguments: map[string]any{"name": "you"},
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}
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res, err := session.CallTool(ctx, params)
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if err != nil {
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log.Fatalf("CallTool failed: %v", err)
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}
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if res.IsError {
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log.Fatal("tool failed")
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}
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for _, c := range res.Content {
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log.Print(c.(*mcp.TextContent).Text)
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}
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}
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```
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Here's an example of the corresponding server component, which communicates
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with its client over stdin/stdout:
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```go
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package main
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import (
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"context"
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"log"
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"github.com/modelcontextprotocol/go-sdk/mcp"
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)
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type HiParams struct {
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Name string `json:"name" jsonschema:"the name of the person to greet"`
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}
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func SayHi(ctx context.Context, req *mcp.ServerRequest[*mcp.CallToolParamsFor[HiParams]]) (*mcp.CallToolResultFor[any], error) {
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return &mcp.CallToolResultFor[any]{
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Content: []mcp.Content{&mcp.TextContent{Text: "Hi " + req.Params.Arguments.Name}},
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}, nil
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}
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func main() {
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// Create a server with a single tool.
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server := mcp.NewServer(&mcp.Implementation{Name: "greeter", Version: "v1.0.0"}, nil)
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mcp.AddTool(server, &mcp.Tool{Name: "greet", Description: "say hi"}, SayHi)
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// Run the server over stdin/stdout, until the client disconnects
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if err := server.Run(context.Background(), &mcp.StdioTransport{}); err != nil {
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log.Fatal(err)
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}
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}
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```
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The [`examples/`](/examples/) directory contains more example clients and servers.
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## Acknowledgements
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Several existing Go MCP SDKs inspired the development and design of this
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official SDK, notably [mcp-go](https://github.com/mark3labs/mcp-go), authored
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by Ed Zynda. We are grateful to Ed as well as the other contributors to mcp-go,
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and to authors and contributors of other SDKs such as
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[mcp-golang](https://github.com/metoro-io/mcp-golang) and
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[go-mcp](https://github.com/ThinkInAIXYZ/go-mcp). Thanks to their work, there
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is a thriving ecosystem of Go MCP clients and servers.
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## License
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This project is licensed under the MIT License - see the [LICENSE](./LICENSE)
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file for details.
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