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# MCP Go SDK
[](https://codespaces.new/modelcontextprotocol/go-sdk)
[](https://pkg.go.dev/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 |
|-----------------|-------------------|------------------------------------------------|
| v1.2.0+ | 2025-06-18 | 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 |
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.
