Alexa Subscribe MQTT

Hi guys, I'm new developing Alexa skills and I'm having trouble receiving data via MQTT. I'm sending a json from ESP32 to a IoT rule that trigger AWS Lambda where my skill is linked but I don't understand how I choose which method will be executed or how I should format a JSON to trigger an specific intent. The general idea would be, I send a command to ESP32 after the user's command and after ESP32 finishes what was asked to return an "OK" and Alexa tells the user some message. I tried to find some tutorial or document but I couldn't find it. Thanks for the help.