Right now device related API calls return a string value named uuid. The API documentation says:
The internal unique device UUID. Make sure to keep this ID a secret as it can be used to access all information related to this Pi without further authentication. It still doesn’t allow access to your account but someone with access to this ID can fetch all current and future files assigned to this device from the info-beamer storage service, just like the device itself does.
This uuid was never really useful for anything except maybe uniquely identifying a single device. The id field, the device id, already offers that property and has always been included and used as the primary key for identifying any device in other calls.
The uuid is mostly used internally and increasingly as a shared secret between the device and the info-beamer service itself. Exposing it in these API calls adds more risks than benefits. So it makes sense to removed the uuid field from all device related calls after July 1st. This includes /device/<device-id> and /device/list calls.
The migration is pretty easy: Anything that currently uses the uuid as a unique key to identify a device can use the stringified id field instead. Both are returned in all device calls and are guaranteed to uniquely identify a device.
Please get in contact, should you rely on the uuid field at the moment or need help with these changes.