Rails Dev MCP

A Model Context Protocol (MCP) server that allows AI agents to manage Rails development servers. Start, stop, and monitor your Rails app directly from Claude!

Features

• start_dev_server: Start Rails development server on a specified port
• stop_dev_server: Stop the running Rails server
• dev_server_logs: View recent logs and notable events (errors, warnings, requests)
• dev_server_status: Check if the server is running and get connection details

Installation

As a gem

gem install rails-dev-mcp

From source

git clone https://github.com/obie/rails-dev-mcp.git
cd rails-dev-mcp
bundle install
rake install

Usage

With Claude Desktop

Add to your Claude Desktop configuration (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "rails-dev": {
      "command": "rails-dev-mcp",
      "cwd": "/path/to/your/rails/project"
    }
  }
}

With ClaudeOnRails

The Rails Dev MCP integrates seamlessly with ClaudeOnRails. Add to your claude-swarm.yml:

mcps:
  - name: rails-dev
    type: stdio
    command: rails-dev-mcp
    args: []

Available Tools

start_dev_server

Starts the Rails development server.

Parameters:

• port (optional): Port number (default: 3000)

Example:

Start the Rails server on port 3001

stop_dev_server

Stops the running Rails development server.

Example:

Stop the Rails server

dev_server_logs

Retrieves recent logs from the Rails server.

Parameters:

• lines (optional): Number of log lines to retrieve (default: 50)
• notable_only (optional): Show only errors, warnings, and requests

Example:

Show me the last 100 lines from the Rails server logs
Show me only errors from the Rails logs

dev_server_status

Checks the current status of the Rails development server.

Example:

Is the Rails server running?

How It Works

1. Process Management: Uses Ruby's Open3 to manage the Rails server process
2. Log Capture: Redirects server output to a log file for later retrieval
3. PID Tracking: Maintains PID files to track running processes
4. Smart Log Filtering: Identifies notable events like errors, warnings, and HTTP requests

Development

# Run tests
bundle exec rspec

# Run linter
bundle exec rubocop

# Build gem
gem build rails-dev-mcp.gemspec

License

MIT License - see LICENSE file for details.