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86 changes: 86 additions & 0 deletions blog/content/posts/2026-07-27-ruby-sdk-1-0.md
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---
title: The Official Ruby SDK for MCP Reaches 1.0
date: "2026-07-27T09:00:00+00:00"
publishDate: "2026-07-27T09:00:00+00:00"
slug: ruby-sdk-1-0
description: The official Ruby SDK for the Model Context Protocol has reached version 1.0 with a stable public API and a 100% conformance pass rate. The SDK now meets every Tier 2 requirement of the MCP SDK tiering system, and development toward Tier 1 continues.
author:
- Koichi Ito (Ruby SDK Maintainer)
tags:
- mcp
- sdk
- release
- announcement
- ruby
---

[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

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

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

Install the gem:

```console
$ gem install mcp
```

A minimal stdio server looks like this:

```ruby
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

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.
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