3da831b0c9* mcp: move to 2025-06-18 schema Add types and fields for the latest MCP schema. The main challenge here was dealing with the presence of _meta fields on many types, like Tool, Prompt and Resource. - Distinguish between the _meta field of a request's params, which includes a progress token, from the _meta field on other types, which is simply a map. - Redefine GetMeta to return a pointer to the map. We wanted to avoid that, but I don't see a clean way to do so. An alternative would be to have GetMeta return a map, and SetMeta to set it. - Provide GetProgressToken for requests only (not notifications or other types). - Still to do: deal with the meta and annotation fields of ContentBlock, which are currently duplicated for Resource and ResourceContents. * Meta and progress token redesign
148 lines
4.3 KiB
Markdown
148 lines
4.3 KiB
Markdown
<!-- Autogenerated by weave; DO NOT EDIT -->
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# MCP Go SDK
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<!-- TODO: update pkgsite links here to point to the modelcontextprotocol
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module, once it exists. -->
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[](https://pkg.go.dev/github.com/modelcontextprotocol/go-sdk)
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This repository contains an implementation of the official Go software
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development kit (SDK) for the Model Context Protocol (MCP).
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**WARNING**: The SDK is currently unstable and subject to breaking changes.
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Please test it out and file bug reports or API proposals. The [TODO](#todo)
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section below outlines outstanding release blockers. We aim to release a stable
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version of the SDK in August, 2025.
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## Package documentation
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The SDK consists of two 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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## 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-client", "v1.0.0", nil)
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// Connect to a server over stdin/stdout
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transport := mcp.NewCommandTransport(exec.Command("myserver"))
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session, err := client.Connect(ctx, transport)
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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.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"`
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}
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func SayHi(ctx context.Context, cc *mcp.ServerSession, params *mcp.CallToolParamsFor[HiParams]) (*mcp.CallToolResultFor[any], error) {
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return &mcp.CallToolResultFor[any]{
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Content: []*mcp.ContentBlock{mcp.NewTextContent("Hi " + params.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("greeter", "v1.0.0", nil)
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server.AddTools(mcp.NewServerTool("greet", "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.NewStdioTransport()); 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/` directory contains more example clients and servers.
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## TODO
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The following TODOs block the release of this SDK:
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- Better support for resumability in the Streamable HTTP transport: a
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server-side event store and client-side retry configuration.
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- OAuth support (or examples of implementing OAuth using middleware).
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- Support for the changes in the
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[2025-06-18](https://modelcontextprotocol.io/specification/2025-06-18/changelog)
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version of the MCP spec.
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- More examples and documentation.
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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 GitHub issues. See CONTRIBUTING.md
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for details.
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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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