ActionMCP

What is ActionMCP?

ActionMCP is a Ruby gem that provides Model Context Protocol (MCP) server capability to Ruby on Rails applications. It is designed for production Rails environments and supports network-based deployments only (STDIO transport is not supported). The gem offers base classes and helpers so developers can focus on their app’s logic while ActionMCP handles MCP compliance.

How to use ActionMCP?

Add the gem to your Gemfile with bundle add actionmcp, run bundle install, copy migrations with bin/rails action_mcp:install:migrations, generate base classes and configuration with bin/rails generate action_mcp:install, then run bin/rails db:migrate. Subclass the provided Prompt, Tool, and ResourceTemplate classes to expose your app’s functionality to LLMs.

Key features of ActionMCP

• Provides base classes for Prompt, Tool, and ResourceTemplate.
• Supports MCP 2025-06-18 with backward compatibility to 2025-03-26.
• Full JSON‑RPC 2.0 transport layer with capability negotiation.
• Consent management for sensitive tool operations.
• Structured output via output_schema and resource_link support.
• Task‑augmented tools with async execution and progress updates.

Use cases of ActionMCP

• Build a production‑ready MCP server for a Ruby on Rails application.
• Expose custom prompts and tools to large language models via MCP.
• Implement consent‑gated operations like file system access or database modifications.
• Create asynchronous tasks that report progress for long‑running indexing or processing.

FAQ from ActionMCP

What MCP protocol versions does ActionMCP support?

ActionMCP supports MCP 2025‑06‑18 (current) and is backward compatible with MCP 2025‑03‑26.

Does ActionMCP support STDIO transport?

No. STDIO is intentionally excluded because it is not production‑ready; ActionMCP is built for robust, network‑based deployments.

What are the runtime requirements for ActionMCP?

Ruby 3.4.8+ or 4.0.0+, Rails 8.1.1+, and a PostgreSQL, MySQL, or SQLite3 database.

How do I install ActionMCP?

Add the gem (bundle add actionmcp), install dependencies, copy migrations, run the install generator, and migrate the database. See the Installation section for full steps.

How does consent management work for tools?

Tools marked with requires_consent! require explicit user consent before execution. Consent is session‑scoped and can be granted or revoked via the session object.