mcp_golang

mcp-golang

mcp-golang is an unofficial implementation of the Model Context Protocol in Go.

Write MCP servers in golang with a few lines of code.

Docs at https://mcpgolang.com

Highlights

• 🛡️Type safety - Define your tool arguments as native go structs, have mcp-golang handle the rest. Automatic schema generation, deserialization, error handling etc.
• 🚛 Custom transports - Use the built-in transports or write your own.
• ⚡ Low boilerplate - mcp-golang generates all the MCP endpoints for you apart from your tools, prompts and resources.
• 🧩 Modular - The library is split into three components: transport, protocol and server. Use them all or take what you need.

Example Usage

package main

import (
	"fmt"
	"github.com/metoro-io/mcp-golang"
	"github.com/metoro-io/mcp-golang/transport/stdio"
)

// Tool arguments are just structs, annotated with jsonschema tags
// More at https://mcpgolang.com/tools#schema-generation
type Content struct {
	Title       string  `json:"title" jsonschema:"required,description=The title to submit"`
	Description *string `json:"description" jsonschema:"description=The description to submit"`
}
type MyFunctionsArguments struct {
	Submitter string  `json:"submitter" jsonschema:"required,description=The name of the thing calling this tool (openai, google, claude, etc)"`
	Content   Content `json:"content" jsonschema:"required,description=The content of the message"`
}

func main() {
	done := make(chan struct{})

	server := mcp_golang.NewServer(stdio.NewStdioServerTransport())
	err := server.RegisterTool("hello", "Say hello to a person", func(arguments MyFunctionsArguments) (*mcp_golang.ToolResponse, error) {
		return mcp_golang.NewToolResponse(mcp_golang.NewTextContent(fmt.Sprintf("Hello, %server!", arguments.Submitter))), nil
	})
	if err != nil {
		panic(err)
	}

	err = server.RegisterPrompt("promt_test", "This is a test prompt", func(arguments Content) (*mcp_golang.PromptResponse, error) {
		return mcp_golang.NewPromptResponse("description", mcp_golang.NewPromptMessage(mcp_golang.NewTextContent(fmt.Sprintf("Hello, %server!", arguments.Title)), mcp_golang.RoleUser)), nil
	})
	if err != nil {
		panic(err)
	}

	err = server.RegisterResource("test://resource", "resource_test", "This is a test resource", "application/json", func() (*mcp_golang.ResourceResponse, error) {
		return mcp_golang.NewResourceResponse(mcp_golang.NewTextEmbeddedResource("test://resource", "This is a test resource", "application/json")), nil
	})

	err = server.Serve()
	if err != nil {
		panic(err)
	}

	<-done
}

This will start a server using the stdio transport (used by claude desktop), host a tool called "hello" that will say hello to the user who submitted it.

You can use raw go structs as the input to your tools, the library handles generating the messages, deserialization, etc.

Contributions

Contributions are more than welcome! Please check out our contribution guidelines.

Discord

Got any suggestions, have a question on the api or usage? Ask on the discord server. A maintainer will be happy to help you out.

Examples

Some more extensive examples using the library found here:

• Metoro - Query and interact with kubernetes environments monitored by Metoro

Open a PR to add your own projects!

Server Feature Implementation

Tools

• Tool Calls
• Native go structs as arguments
• Programatically generated tool list endpoint
• Change notifications
• Pagination

Prompts

• Prompt Calls
• Programatically generated prompt list endpoint
• Change notifications
• Pagination

Resources

• Resource Calls
• Programatically generated resource list endpoint
• Change notifications
• Pagination

Transports

• Stdio
• SSE
• Custom transport support
• HTTPS with custom auth support - in progress. Not currently part of the spec but we'll be adding experimental support for it.