The Official Ruby SDK for MCP Reaches 1.0

Version 1.0.0 of the official Ruby SDK for the Model Context Protocol is now available, marking the first stable release of the mcp gem with a stable public API and Semantic Versioning. The SDK now meets every Tier 2 requirement of the SDK tiering system, passing 100% of server and client conformance scenarios, and implements the 2025-06-18 and 2025-11-25 specification revisions. The release includes MCP servers with tools, prompts, resources, and more, plus a client with complete OAuth flow and stdio and Streamable HTTP transports.

Version 1.0.0 https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v1.0.0 of the official Ruby SDK https://github.com/modelcontextprotocol/ruby-sdk for the Model Context Protocol is now available. This is the first stable release of the mcp gem https://rubygems.org/gems/mcp : the public API is now stable, and breaking changes ship only in major releases, following the Semantic Versioning policy documented in VERSIONING.md https://github.com/modelcontextprotocol/ruby-sdk/blob/main/VERSIONING.md . Alongside the release, the Ruby SDK now meets every Tier 2 requirement of the SDK tiering system https://modelcontextprotocol.io/community/sdk-tiers , as recorded in the Tier 2 assessment https://github.com/modelcontextprotocol/modelcontextprotocol/issues/3127 , and development toward Tier 1 is ongoing. What is in 1.0 what-is-in-10 The 1.0 release implements the 2025-06-18 and 2025-11-25 specification revisions and passes 100% of the server and client conformance scenarios. It includes: - MCP servers with tools, prompts, resources including templates and subscriptions , completions, logging, pagination, progress, and cancellation, plus server-to-client requests for sampling, elicitation form and URL mode , and roots - An MCP client with a complete OAuth flow, including dynamic client registration, PKCE, and scope handling - stdio and Streamable HTTP transports; the HTTP transport is a standard Rack app, so it can be mounted directly in Rails routes or any Rack-compatible framework From Tier 3 to Tier 2 from-tier-3-to-tier-2 The Ruby SDK was assessed at Tier 3 https://github.com/modelcontextprotocol/modelcontextprotocol/issues/2340 in March 2026. Since then: - Server conformance moved from 83.3% to 100%, with no baselined failures - A conformance client was implemented and passes 100% of client scenarios - Sampling, elicitation, and progress notifications were implemented on both the server and client sides ROADMAP.md https://github.com/modelcontextprotocol/ruby-sdk/blob/main/ROADMAP.md and VERSIONING.md https://github.com/modelcontextprotocol/ruby-sdk/blob/main/VERSIONING.md were published Work is also under way to support the upcoming 2026-07-28 specification release /posts/sdk-betas-2026-07-28/ . Get started get-started Install the gem: bash $ gem install mcp A minimal stdio server looks like this: require "mcp" class ExampleTool < MCP::Tool description "A simple example tool that echoes back its arguments" input schema properties: { message: { type: "string" }, }, required: "message" class << self def call message:, server context: MCP::Tool::Response.new { type: "text", text: "Hello from example tool Message: {message}", } end end end server = MCP::Server.new name: "example server", tools: ExampleTool , MCP::Server::Transports::StdioTransport.new server .open See the Ruby SDK documentation https://ruby.sdk.modelcontextprotocol.io for guides on building servers and clients, including Rails integration. Give us your feedback give-us-your-feedback If you run into problems or unexpected behavior while using the SDK, please report them on the issue tracker https://github.com/modelcontextprotocol/ruby-sdk/issues . Reports from real-world usage are especially valuable. The Ruby SDK began at Shopify https://www.shopify.com/ and is maintained by Topher Bullock https://github.com/topherbullock , Koichi Ito https://github.com/koic , Ateş Göral https://github.com/atesgoral , and Jonathan Hefner https://github.com/jonathanhefner together with the wider Ruby community. Thank you to everyone for the feedback and contributions on the road to 1.0.