Ruby MCP SDK

The official Ruby SDK for Model Context Protocol servers and clients.
Detailed guides are available at https://ruby.sdk.modelcontextprotocol.io.
Features
- Build MCP servers that expose tools, prompts, and resources to any MCP host, with OAuth 2.1 resource-server protection
- Build MCP clients that connect to any MCP server, with automatic lifecycle negotiation and OAuth 2.1 authorization
- Speak every standard transport: stdio and Streamable HTTP (including SSE), with a Rails integration
- Cover the full protocol surface: server-to-client requests, multi round-trip requests, notifications, progress, logging, cancellation, completions, and pagination
Installation
Add this line to your application's Gemfile:
And then execute:
Or install it yourself as:
You may need to add additional dependencies depending on which features you wish to access.
Quick Start
The following minimal programs show both sides of the protocol: a server that exposes a single tool,
and a client that spawns such a server and drives it over stdio.
MCP Server
A minimal server defines a tool and serves it over the stdio transport:
The same client can connect to Streamable HTTP servers with MCP::Client::HTTP;
see Client Transports.
Examples
Runnable examples are available in examples,
including a complete Rails application in examples/rails.
Documentation
- SDK guides
- SDK API documentation
- Model Context Protocol documentation
License
This project is licensed under the Apache License 2.0 for new contributions, with existing code under MIT. See the LICENSE file for details.