🤔 What is go‑mcp? • ✨ Features • 🏁 Quick Start • 🔍 Examples • ✅ Supported Features • 🤝 Contributing
go‑mcp is a Go SDK for building MCP (Model Context Protocol) servers with ease and confidence. It provides a type‑safe, intuitive interface that makes server development a breeze.
- 🔒 Type‑Safe – Code generation ensures your tools and prompt parameters are statically typed, so errors are caught at compile time instead of at runtime.
- 🧩 Simple & Intuitive API – A natural, idiomatic Go interface that lets you build servers quickly without a steep learning curve.
- 🔌 Developer‑Friendly – Designed with API ergonomics in mind, making it approachable.
Creating an MCP server with go‑mcp is straightforward!
Below is an example directory structure for a temperature‑conversion MCP server:
.
├── cmd
│ ├── mcpgen
│ │ └── main.go
│ └── temperature
│ └── main.go
├── mcp.gen.go
└── temperature.go
First, create cmd/mcpgen/main.go for code generation. Running this file will automatically generate the necessary code.
package main
import (
"log"
"os"
"path/filepath"
"github.com/ktr0731/go-mcp/codegen"
)
func main() {
// Create output directory
outDir := "."
if err := os.MkdirAll(outDir, 0o755); err != nil {
log.Fatalf("failed to create output directory: %v", err)
}
// Create output file
f, err := os.Create(filepath.Join(outDir, "mcp.gen.go"))
if err != nil {
log.Fatalf("failed to create file: %v", err)
}
defer f.Close()
// Server definition
def := &codegen.ServerDefinition{
Capabilities: codegen.ServerCapabilities{
Tools: &codegen.ToolCapability{},
Logging: &codegen.LoggingCapability{},
},
Implementation: codegen.Implementation{
Name: "Temperature MCP Server",
Version: "1.0.0",
},
// Tool definitions (declared with Go structs)
Tools: []codegen.Tool{
{
Name: "convert_temperature",
Description: "Convert temperature between Celsius and Fahrenheit",
InputSchema: struct {
Temperature float64 `json:"temperature" jsonschema:"description=Temperature value to convert"`
FromUnit string `json:"from_unit" jsonschema:"description=Source temperature unit,enum=celsius,enum=fahrenheit"`
ToUnit string `json:"to_unit" jsonschema:"description=Target temperature unit,enum=celsius,enum=fahrenheit"`
}{},
},
},
}
// Generate code
if err := codegen.Generate(f, def, "temperature"); err != nil {
log.Fatalf("failed to generate code: %v", err)
}
}Generate the code:
Next, implement the server logic in cmd/temperature/main.go:
package main
import (
"context"
"fmt"
"log"
"math"
mcp "github.com/ktr0731/go-mcp"
"golang.org/x/exp/jsonrpc2"
)
type toolHandler struct{}
func (h *toolHandler) HandleToolConvertTemperature(ctx context.Context, req *ToolConvertTemperatureRequest) (*mcp.CallToolResult, error) {
temperature := req.Temperature
fromUnit := req.FromUnit
toUnit := req.ToUnit
var result float64
switch {
case fromUnit == ConvertTemperatureFromUnitTypeCelsius && toUnit == ConvertTemperatureToUnitTypeFahrenheit:
// °C → °F: (C × 9/5) + 32
result = (temperature*9/5 + 32)
case fromUnit == ConvertTemperatureFromUnitTypeFahrenheit && toUnit == ConvertTemperatureToUnitTypeCelsius:
// °F → °C: (F − 32) × 5/9
result = (temperature - 32) * 5 / 9
case fromUnit == toUnit:
result = temperature
default:
return nil, fmt.Errorf("unsupported conversion: %s to %s", fromUnit, toUnit)
}
// Round to two decimal places
result = math.Round(result*100) / 100
resultText := fmt.Sprintf("%.2f %s = %.2f %s", temperature, fromUnit, result, toUnit)
return &mcp.CallToolResult{
Content: []mcp.CallToolContent{
mcp.TextContent{Text: resultText},
},
}, nil
}
func main() {
handler := NewHandler(&toolHandler{})
ctx, listener, binder := mcp.NewStdioTransport(context.Background(), handler, nil)
srv, err := jsonrpc2.Serve(ctx, listener, binder)
if err != nil {
log.Fatalf("failed to serve: %v", err)
}
srv.Wait()
}Run the server:
See complete examples in the examples directory and the API documentation.
- Ping
- Tools
- Prompts
- Prompts, Tools, Resources, Resource Templates
- Resource subscription
- Resource update notification
- Logging
- Completion
- Cancellation
🚧 Under Development
- Batching (JSON‑RPC 2.0)
- Streamable HTTP transport
- Progress notification
🚫 Not Planned
-
Dynamic prompt and tool changes
Go is not well‑suited for dynamic tool additions. Adding tools dynamically requires constructing tool definitions, JSON Schema, and handlers at runtime. While generated code remains type‑safe, dynamically added components do not, forcing heavy use of
anyand type assertions and harming interface consistency. We delegate these use cases to SDKs in languages better suited for dynamic changes, such as TypeScript.Most currently implemented MCP servers use static definitions only, and dynamic changes do not seem to be a primary use case yet.
Contributions are welcome! Feel free to submit a pull request.
This project is licensed under the MIT License – see the LICENSE file for details.