A simple Ruby on Rails application demonstrating how to integrate and use the ActionMCP gem. The gem source code can be found on GitHub at https://github.com/seuros/mcp.
This application showcases how to define and use MCP components within a Rails project.
- Ruby (see
.ruby-versionfor recommended version) - PostgreSQL (or Docker)
git clone https://github.com/seuros/mcp_rails_template.git
cd mcp_rails_template
bin/setupCopy the provided .env.example file:
cp .env.example .envEdit .env and fill in necessary values according to your setup (especially any required API keys for tools like fetch_weather_by_location_tool).
You can quickly spin up a temporary PostgreSQL instance using Docker:
make upThis will start PostgreSQL on port 5466.
Alternatively, configure your own PostgreSQL database by editing config/database.yml.
Launch the Rails server:
bin/rails sThe app will be available at http://localhost:3002.
ActionMCP runs as a standalone server on port 62770 (via mcp.ru). Nginx proxies /mcp requests to this server.
Client → nginx:8080/mcp → ActionMCP:62770
This application uses JWT-based authentication via the ApplicationGateway class.
| Password | Role | |
|---|---|---|
| test@example.com | password123 | Test User |
| admin@example.com | password123 | Admin User |
bin/rails db:fixtures:load FIXTURES=users# In Rails console
user = User.find_by(email: 'test@example.com')
token = user.generate_jwt(expires_in: 10.years) # Long-lived for demoA .mcp.json file is provided with a pre-configured long-lived token:
{
"mcpServers": {
"mcp_rails_template": {
"url": "http://localhost:8080/mcp",
"headers": {
"Authorization": "Bearer <token>"
}
}
}
}Or test manually with curl:
curl -H "Authorization: Bearer <token>" http://localhost:8080/mcpThe gateway is configured in config/mcp.yml:
development:
authentication: ["jwt"]
gateway_class: "ApplicationGateway"class MyTool < ApplicationMCPTool
def perform
render text: "Hello #{current_user.name}!"
end
endThis application includes several examples of ActionMCP components:
epic_adventure_prompt.rb: Generates a short, narrative adventure story based on a provided hero name and adventure type (fantasy, sci-fi, mystery). It can optionally include a placeholder image data string.
gemfile_template.rb: Provides access to the project's Gemfile dependencies as a JSON resource. It uses Bundler to fetch gems based on the specified environment (production,test,development, ordefault). The resource URI follows the patterngemfile://{environment}.
Tools define specific actions that a language model can request to be executed.
dependency_info_tool.rb: Retrieves dependency information using Bundler from theGemfileandGemfile.lock. It also checks for a.gemspecfile for runtime dependencies. It outputs separate JSON resources forproduction,test, andruntimedependencies.fetch_weather_by_location_tool.rb: Fetches weather forecast data from the Open-Meteo API (https://api.open-meteo.com) based on provided latitude and longitude coordinates. It returns the raw JSON response from the API.rubocop_tool.rb: Analyzes a provided Ruby code snippet using the RuboCop gem's API. It reports any detected style or code quality offenses, including the rule name, message, line, and column number.ruby_code_analyzer_tool.rb: Performs basic static analysis of Ruby code within the project directory. It indexes classes, modules, and methods by parsing.rbfiles. It can be queried to list all found classes, modules, or methods, or to get details (including source snippets) for a specific class/module (constant) or method (method_details).
To test and inspect MCP functionality interactively, you can use the MCP Inspector:
npx @modelcontextprotocol/inspector --url http://localhost:8080/mcpMake sure Docker is running (docker compose up) before executing the inspector command.
Feel free to contribute! Open issues or submit pull requests to help improve this example.
Happy Coding! ✨🚀