SmartThings Hub "notify" endpoint?

I’m attempting to make LAN Connected Devices. The documentation says I can have the SmartHub receive notifications from the device. However, I’m not finding any documentation on what the /notify endpoint expects to receive. Does anyone know where the documentation for this is located?

I’m essentially trying to implement a real time version of the Refresh capability.

The endpoint is implemented primarily to receive UPnP notifications, but it should receive any correctly formatted HTTP request (e.g. POST). You cannot return any response from the hub through it though.