Where to find the Zigbee API for a device?


Suppose I want to write an app to support a zigbee device. I’ll manage to write the app (some topics available on the forum here too), but where do I find information on how to communicate with the device? Do I need an API from the manufacturer? Is it possible to reverse engineer the Zigbee “commands”? Can you sniff Zigbee?


I think you just read the developer informations.