akhilraghav0/hamr

hamr Build MCP servers in Go. Optimized for token cost.

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What is this?

MCP (Model Context Protocol) lets AI assistants like Claude, Cursor, and Windsurf call external tools. An MCP server is basically a plugin that gives AI the ability to do things — query your database, check your Kubernetes cluster, search your codebase, whatever you need.

The problem is that building an MCP server in Go means writing a ton of boilerplate. You have to manually define JSON schemas, handle JSON-RPC framing, parse and validate inputs, wire up transport, manage errors — and you end up with 200+ lines of ceremony before you even get to your actual logic.

hamr fixes that. You write a Go struct for your input, a function for your logic, and one line to register it. hamr handles everything else — schema generation, validation, transport, middleware, the whole protocol. Your struct tags are your schema.

Think of it like Cobra but for MCP servers instead of CLI apps.

Show me the code

Here’s a complete, working MCP server:

package main

import (
    "context"
    "log"

    "github.com/AKhilRaghav0/hamr"
)

type SearchInput struct {
    Query      string `json:"query" desc:"search query"`
    MaxResults int    `json:"max_results" desc:"max results" default:"10"`
    Format     string `json:"format" desc:"output format" enum:"json,text,csv"`
}

func Search(ctx context.Context, input SearchInput) (string, error) {
    // your actual search logic here
    return "results for: " + input.Query, nil
}

func main() {
    s := hamr.New("my-server", "1.0.0")
    s.Tool("search", "Search for information", Search)
    log.Fatal(s.Run())
}