Content
MCP Go SDK
==========
[](https://github.com/cavernouskina/mcp-go/actions/workflows/ci.yml)
[](https://goreportcard.com/report/github.com/cavernouskina/mcp-go)
[](https://pkg.go.dev/github.com/cavernouskina/mcp-go)
A Go implementation of the [Model Context Protocol](https://modelcontextprotocol.io) (MCP), providing both client and server capabilities for integrating with LLM surfaces.
## Overview
The Model Context Protocol allows applications to provide context for LLMs in a standardized way, separating the concerns of providing context from the actual LLM interaction. This Go SDK implements the full MCP specification, making it easy to:
- Build MCP clients that can connect to any MCP server
- Create MCP servers that expose resources, prompts and tools
- Use standard transports like stdio and SSE (coming soon)
- Handle all MCP protocol messages and lifecycle events
## A small example
Curious what all this looks like in practice? Here's an example server that
exposes the contents of an `io.FS` as resources.
```go
package main
import (
"context"
"flag"
"io/fs"
"log"
"mime"
"os"
"path/filepath"
"strings"
"github.com/cavernouskina/mcp-go"
)
type FSServer struct {
fs fs.FS
mcp.UnimplementedServer
}
func (s *FSServer) Initialize(ctx context.Context, req *mcp.Request[mcp.InitializeRequest]) (*mcp.Response[mcp.InitializeResponse], error) {
return mcp.NewResponse(&mcp.InitializeResponse{
ProtocolVersion: req.Params.ProtocolVersion,
Capabilities: mcp.ServerCapabilities{
Resources: &mcp.Resources{},
},
}), nil
}
func (s *FSServer) ListResources(ctx context.Context, req *mcp.Request[mcp.ListResourcesRequest]) (*mcp.Response[mcp.ListResourcesResponse], error) {
var resources []mcp.Resource
fs.WalkDir(s.fs, ".", func(path string, d fs.DirEntry, err error) error {
if err != nil {
return err
}
if d.IsDir() {
return nil
}
resources = append(resources, mcp.Resource{
URI: "file://" + path,
Name: path,
MimeType: mime.TypeByExtension(filepath.Ext(path)),
})
return nil
})
return mcp.NewResponse(&mcp.ListResourcesResponse{
Resources: resources,
}), nil
}
func (s *FSServer) ReadResource(ctx context.Context, req *mcp.Request[mcp.ReadResourceRequest]) (*mcp.Response[mcp.ReadResourceResponse], error) {
contents, err := fs.ReadFile(s.fs, strings.TrimPrefix(req.Params.URI, "file://"))
if err != nil {
return nil, err
}
return mcp.NewResponse(&mcp.ReadResourceResponse{
Contents: []mcp.ResourceContent{
{
URI: req.Params.URI,
MimeType: mime.TypeByExtension(filepath.Ext(req.Params.URI)),
Text: string(contents), // TODO: base64 encode
},
},
}), nil
}
func main() {
flag.Parse()
root := flag.Arg(0)
if root == "" {
root = "/"
}
server := mcp.NewStdioServer(&FSServer{
fs: os.DirFS(root),
})
if err := server.Listen(context.Background(), os.Stdin, os.Stdout); err != nil {
log.Fatal(err)
}
}
```
You can compile this example and wire it up to Claude Desktop (or any other MCP client).
```json
{
"mcpServers": {
"fs": {
"command": "/path/to/mcp-go-fs",
"args": [
"/path/to/root/directory"
]
}
}
}
```
## Documentation
- [Model Context Protocol documentation](https://modelcontextprotocol.io)
- [MCP Specification](https://spec.modelcontextprotocol.io)
- [Example Servers](https://github.com/cavernouskina/mcp-go/tree/main/examples)
## Roadmap
The majority of the base protocol is implemented. The following features are on our roadmap:
- Notifications
- Sampling
- Roots
## Legal
Offered under the [MIT license](LICENSE).
