Rails MCP Server

What is Rails MCP Server?

Rails MCP Server is a Ruby implementation of the Model Context Protocol (MCP) for Rails projects. It allows Large Language Models (LLMs) to perform code analysis, exploration, and development assistance on Rails applications through a standardized protocol.

How to use Rails MCP Server?

Install the gem (gem install rails-mcp-server) and run the interactive configuration tool (rails-mcp-config) to manage projects and download documentation. Start the server in STDIO mode (default) or HTTP mode (rails-mcp-server --mode http). Integrate with Claude Desktop via the configuration tool or by editing claude_desktop_config.json. For GitHub Copilot, create a .github/copilot/mcp.json file pointing to the server.

Key features of Rails MCP Server

• Manage multiple Rails projects simultaneously
• Browse files, routes, models, schema, and controller–view relationships
• Execute sandboxed Ruby code for custom queries
• Access Rails, Turbo, Stimulus, and Kamal documentation
• Context-efficient progressive tool discovery (4 bootstrap tools)
• Run in STDIO or HTTP (JSON‑RPC + SSE) mode
• Automatic Claude Desktop and GitHub Copilot Agent integration

Use cases of Rails MCP Server

• AI‑powered code understanding and navigation in Rails applications
• Automated database schema and model relationship analysis
• Developer assistance with sandboxed Ruby execution
• Configuration audit and environment analysis across projects

FAQ from Rails MCP Server

What are the runtime dependencies?

Ruby is required. The optional Gum tool enhances the interactive configuration UI but is not mandatory.

What communication modes are supported?

The server supports STDIO mode (default for direct LLM client integration) and HTTP mode with JSON‑RPC and Server‑Sent Events (SSE) endpoints.

Where are configuration files stored?

The server follows the XDG Base Directory Specification. On macOS, files are in ~/.config/rails-mcp (or $XDG_CONFIG_HOME/rails-mcp); on Windows, in %APPDATA%\rails-mcp. A projects.yml file lists the managed Rails projects.

What are the limitations with GitHub Copilot?

GitHub Copilot Agent only supports MCP tools (not resources or prompts). The load_guide analyzer works via execute_tool but requires guides to be downloaded during setup.

How does security work in HTTP mode?

By default the server binds only to localhost. The --bind-all flag allows local‑network access but includes built‑in security features (origin and IP validation). Only use this on trusted networks.