MCP Rb

🚀 MCP-RB

A lightweight Ruby framework for implementing MCP (Model Context Protocol) servers with a Sinatra-like DSL style.

🚀 Quick Start

✨ Features

MCP-RB is a lightweight Ruby framework that allows you to implement MCP servers. It features a Sinatra-like DSL style, making it easy to define resources, resource templates, and tools.

📦 Installation

Add the following line to your application's Gemfile:

gem 'mcp-rb'

💻 Usage Examples

Basic Usage

Here is a simple example of creating an MCP server:

require 'mcp'

name "hello-world"

version "1.0.0"

# Define a resource
resource "hello://world" do
  name "Hello World"
  description "A simple 'Hello, World!' message"
  call { "Hello, World!" }
end

# Define a resource template
resource_template "hello://{user_name}" do
  name "Hello User"
  description "A simple message to greet a user"
  call { |args| "Hello, #{args[:user_name]}!" }
end

# Define a tool
tool "greet" do
  description "Greet someone by name"
  argument :name, String, required: true, description: "The name to greet"
  call do |args|
    "Hello, #{args[:name]}!"
  end
end

# Define a tool with nested parameters
tool "greet_full_name" do
  description "Greet someone by full name"
  argument :person, required: true, description: "The person to greet" do
    argument :first_name, String, required: false, description: "The first name"
    argument :last_name, String, required: false, description: "The last name"
  end
  call do |args|
    "Hello, First Name: #{args[:person][:first_name]} Last Name: #{args[:person][:last_name]}!"
  end
end

# Define a tool with an Array parameter
tool "group_greeting" do
  description "Greet multiple people at once"
  argument :people, Array, required: true, items: String, description: "The people to greet"
  call do |args|
    args[:people].map { |person| "Hello, #{person}!" }.join(", ")
  end
end

📚 Documentation

Supported Specifications

Refer to: MCP 2024-11-05

• Basic Protocol
  • ping
  • stdio transport
• Server Features
  • Resources
    • resources/read
    • resources/list
    • resources/templates/list
  • Tools
    • tools/list
    • tools/call

Features that are not yet supported are not listed.

Testing

rake test
rake test:unit # Run only unit tests, skip testing the actual running server

Test using MCP Inspector:

bunx @modelcontextprotocol/inspector $(pwd)/examples/hello_world.rb

Formatting

bundle exec standardrb --fix

You can also use rake tasks:

rake lint      # Check code style using standardrb
rake lint:fix  # Automatically fix standardrb issues

Publishing

To publish a new version:

1. Update the version number in lib/mcp/version.rb
2. Update CHANGELOG.md
3. Create a git tag

git add .
git commit -m "Release v.x.y.z"
git tag v.x.y.z
git push --tags

1. Build and push to RubyGems

gem build mcp-rb.gemspec
gem push mcp-rb-*.gem

Changelog

See CHANGELOG.md