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Please reload this page . modelcontextprotocol / ruby-sdk Public * Notifications You must be signed in to change notification settings * Fork 132 * Star 906 * Code * Issues 1 * Pull requests 1 * Discussions * Actions * Projects * Security and quality 7 * Insights Additional navigation options * Code * Issues * Pull requests * Discussions * Actions * Projects * Security and quality * Insights main Branches Tags Go to file Code Open more actions menu Latest commit   History 929 Commits 929 Commits Folders and files Name Name Last commit message Last commit date .github .github     bin bin     conformance conformance     docs docs     examples examples     lib lib     test test     .gitattributes .gitattributes     .gitignore .gitignore     .rubocop.yml .rubocop.yml     AGENTS.md AGENTS.md     CHANGELOG.md CHANGELOG.md     CLAUDE.md CLAUDE.md     CODE_OF_CONDUCT.md CODE_OF_CONDUCT.md     Gemfile Gemfile     LICENSE LICENSE     README.md README.md     RELEASE.md RELEASE.md     ROADMAP.md ROADMAP.md     Rakefile Rakefile     SECURITY.md SECURITY.md     VERSIONING.md VERSIONING.md     dev.yml dev.yml     mcp.gemspec mcp.gemspec     View all files Repository files navigation * * README * Code of conduct * Contributing * License * Security More items MCP Ruby 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 * 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: gem "mcp" And then execute: $ bundle install Or install it yourself as: $ gem install mcp 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: require "mcp" # Create a simple tool 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 # Set up the server server = MCP :: Server . new ( name : "example_server" , tools : [ ExampleTool ] , ) # Create and start the transport transport = MCP :: Server :: Transports :: StdioTransport . new ( server ) transport . open Save the script as server.rb , run it, and send JSON-RPC requests via stdin: $ ruby server.rb {"jsonrpc":"2.0","id":"1","method":"ping"} {"jsonrpc":"2.0","id":"2","method":"tools/list"} {"jsonrpc":"2.0","id":"3","method":"tools/call","params":{"name":"example_tool","arguments":{"message":"Hello"}}} The same server can also run over Streamable HTTP, including mounted inside a Rails application; see Server Transports . MCP Client A minimal client spawns a stdio server as a subprocess, connects, and lists and calls its tools: stdio_transport = MCP :: Client :: Stdio . new ( command : "bundle" , args : [ "exec" , "ruby" , "path/to/server.rb" ] , env : { "API_KEY" => "my_secret_key" } , read_timeout : 30 ) client = MCP :: Client . new ( transport : stdio_transport ) # Perform the MCP initialization handshake before sending any requests. client . connect # List available tools. tools = client . tools tools . each do | tool | puts "Tool: #{ tool . name } - #{ tool . description } " end # Call a specific tool. response = client . call_tool ( tool : tools . first , arguments : { message : "Hello, world!" } ) # Close the transport when done. stdio_transport . close 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. About The official Ruby SDK for the Model Context Protocol servers and clients. ruby.sdk.modelcontextprotocol.io Topics mcp mcp-client mcp-server ruby Resources Readme License Code of conduct Code of conduct Contributing Contributing Security policy Security policy Activity Custom properties Stars 906 stars Watchers 16 watching Forks 132 forks Report repository Releases Used by Contributors Languages Footer (c) 2026 GitHub, Inc. Footer navigation * Terms * Privacy * Security * Status * Community * Docs * Contact * Manage cookies * Do not share my personal information You can’t perform that action at this time.