ActionMCP

ActionMCP – A Production‑Ready MCP Server for Rails

ActionMCP is a Ruby gem that turns any Ruby on Rails application into a fully‑compliant Model Context Protocol (MCP) server. By providing pre‑built base classes, configuration scaffolding, and a network‑oriented transport layer, it removes the boilerplate that would otherwise be required to expose application logic as MCP resources, tools, or prompts. The gem is deliberately focused on production deployments; it does not ship a STDIO transport, which keeps the implementation lean and secure for real‑world use.

The core problem ActionMCP solves is the gap between a Rails codebase and the MCP specification. While MCP defines how an LLM can request data, invoke actions, or receive prompts from an external system, implementing this contract manually is error‑prone and repetitive. ActionMCP supplies a set of abstract classes—, , , and —that encapsulate the JSON‑RPC 2.0 transport, capability negotiation, session handling, and change notification logic described in the MCP 2025‑06‑18 spec. Developers can simply subclass these helpers to expose their own domain logic, and the gem takes care of serializing requests, routing them to the correct handler, and returning properly formatted responses.

Key features include:

• Full MCP compliance with backward compatibility for the 2025‑03‑26 version, ensuring that your server can interoperate with a wide range of LLM clients.
• Robust session management that supports resumable sessions and dynamic capability updates, allowing the server to evolve without breaking existing connections.
• Secure error handling that follows MCP’s prescribed codes (e.g., for method not found, for consent required), giving clients predictable feedback.
• Easy integration into a Rails stack via generators that create configuration files, database migrations, and a conventional directory structure.

In practice, ActionMCP shines in scenarios where an organization wants to expose internal business logic or data repositories to AI assistants. For example, a retail platform can expose inventory queries as MCP tools, allowing an LLM to answer customer questions about stock levels or reorder items. A financial services app can provide a “Generate Report” prompt that triggers complex data aggregation pipelines, all while maintaining the strict request/response contract required by MCP. Because ActionMCP is built on Rails, developers can leverage existing authentication, authorization, and database models to secure MCP endpoints without duplicating effort.

By abstracting the intricacies of the MCP protocol, ActionMCP lets Rails developers focus on their domain logic rather than protocol minutiae. The result is a production‑grade MCP server that integrates seamlessly into AI workflows, supports dynamic capability updates, and ensures consistent, secure communication between large language models and enterprise applications.