RubyMCP - Build a MCP Server with Ruby

A low-level Model-Context-Protocol implementation for Ruby. Supports prompts and completions.

server = RubyMCP::Server.new

server.add_prompt(
  name: "ruby_example",
  description: "Example usage of a method",
  arguments: [
    {
      name: "snippet",
      description: "small ruby snippet",
      required: true,
      completions: ->(*) { [ 'String#split', 'Array#join', 'tally', 'unpack' ] }
    }
  ],
  result: ->(snippet:) {
    {
      description: "Explain '#{snippet}'",
      messages: [
        {
          role: "user",
          content: {
            type: "text",
            text: "              You're a coding assistant in the editor zed.\n              You give one practical example for the given ruby method.\n              Only answer with a single code snippet and one line of explanation.\n              For example:\n              INPUT: '''String#split'''\n              OUTPUT: 'abc'.split('') # ['a', 'b', 'c']\\n Splits the string\"\n            TXT\n          }\n        },\n        {\n          role: \"user\",\n          content: {\n            type: \"text\",\n            text: \"INPUT: '''\#{snippet}'''\"\n          }\n        }\n      ]\n    }\n  },\n)\n\ntransport = RubyMCP::Transport::Stdio.new\nserver.connect(transport)\n"

Logging

RubyMCP supports mcp logging. Each logging level has a corresponding method prefixed with send_ and suffixed with _log_message.

• Debug Level:

  server.send_debug_log_message({ text: "Debug information" })
  

• Info Level:

  server.send_info_log_message({ text: "Informational message" })
  

A MCP client can configure change the log severity or it can be set during server creation. The default is "info".

server = Server.new(logging_verbosity: "debug")