Did you already took a look at our documentation about Actions? Apart from that you may want to look at our example restaurant bot (rasa/examples/restaurantbot at master · RasaHQ/rasa · GitHub). The restaurant bot does not call any other service in the end, but in the actions.py file it defines a RestaurantAPI class (rasa/actions.py at master · RasaHQ/rasa · GitHub), which could execute some API calls to other services. Does that help?