MCP-RB

What is MCP-RB?

MCP-RB is a lightweight Ruby framework for implementing MCP (Model Context Protocol) servers using a Sinatra-like DSL. It integrates with the MCP specification 2024-11-05 and is intended for Ruby developers who want to build MCP servers with minimal boilerplate.

How to use MCP-RB?

Install the gem by adding gem 'mcp-rb' to your Gemfile. In your server script, use the DSL to set the server name and version, then define resources, resource templates, and tools with their callbacks. Run the script directly via a Ruby interpreter; MCP-RB uses stdio transport out of the box.

Key features of MCP-RB

• Sinatra-like DSL for defining server capabilities
• Supports resources, resource templates, and tools
• Tools can accept nested and array arguments
• Implements base protocol (ping), resource endpoints (list, read, templates/list), and tool endpoints (list, call)
• Uses stdio transport only
• Lightweight, Ruby-native implementation

Use cases of MCP-RB

• Building a simple MCP server to expose static resources
• Creating tools that accept complex, structured arguments (e.g., nested hashes or arrays)
• Exposing dynamic, parameterized resources via resource templates
• Rapid prototyping of MCP servers in Ruby
• Testing MCP server behavior with the MCP Inspector tool

FAQ from MCP-RB

Is MCP-RB a server or a framework?

MCP-RB is a Ruby framework that helps you implement an MCP server. You write a script using its DSL and run that script as your server.

What MCP specification version does MCP-RB support?

It targets the MCP 2024-11-05 specification.

What transports does MCP-RB support?

Only stdio transport is supported.

What capabilities are not yet supported?

Any capabilities beyond the base protocol (ping), resources (read, list, templates/list), and tools (list, call) are explicitly not supported.

How can I test an MCP-RB server?

You can run the server with bunx @modelcontextprotocol/inspector or execute the built‑in test suite with rake test.