MicroMcp

MicroMcp is a tiny framework for building MCP servers in Ruby. It ships with a Rust extension that handles the low level protocol while your Ruby code focuses on registering tools.

The gem is available on RubyGems.

Installation

Add the gem to your application's Gemfile:

gem "micro_mcp"

Then execute:

bundle install

Or install it directly with RubyGems:

gem install micro_mcp

Usage

Define one or more tools and start the server:

require "micro_mcp"

 MicroMcp::ToolRegistry.register_tool(name: "say_hello") do
  "Hello World!"
end

# Tools can also accept arguments defined using JSON Schema.
# The arguments hash is provided as the first block parameter.
 MicroMcp::ToolRegistry.register_tool(
  name: "add_numbers",
  description: "Adds two integers",
  arguments: {
    "type" => "object",
    "properties" => {
      "a" => {"type" => "integer"},
      "b" => {"type" => "integer"}
    },
    "required" => ["a", "b"]
  }
) do |args, _runtime|
  (args["a"] + args["b"]).to_s
end

MicroMcp.start_server

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/ekroon/micro_mcp.

License

The gem is available as open source under the terms of the MIT License.