Here is the summary of a refection I had after trying to build a poc for Domoticz. This is not about documenting the code itself, but more how to start.
Maybe it is just about creating the file, and then having everyone contributing to it.

I would be more than happy to handle and challenge the content.

As a library you need to provide some guide on how-to use such library. I tried with #470, but I don't think we understand each other.

Just have a look to https://www.domoticz.com/wiki/Developing_a_Python_plugin which describe the steps on how to develop a plugin in Domoticz.

What I would expect from a Zigpy Developer Guide are:

1- Concepts

• What are the zigpy principle. What does it do (from pairing a device, to handling of messages).
• The usage of asyncio and the development consequences
• how to receive messages from devices (flow)
  • receiving attributes values
  • receiving commands
• how to send command to devices (flow)
• the concept of listner
• How to deal with the Zigbee radio sub libraries
• Zigpy radio schema (which affects configuration options ) - see RFC: Zigpy/API/Radio schemas #381
• how to use quirks

2- My first App using zigpy

• create the PersistentDB and open the zigbee radio (BTW, I don't understand what the 2 are linked together; I would expect (i) PersistentDB (ii) Zigbee radio communication)
• Loading the DB and adding listener
• setting the call back methods

3- API list

4- How to deal with errors