How do interface descriptions work with 802.1x? Will the descriptions remain blank? Will all ports participating in NAC get a generic description? Is it possible to dynamically configure the port description based on the device that is connected to the interface? Other?
Interface descriptions are not affected by 802.1x. Generally 802.1x uses RADIUS A-V (Attribute-Value) pairs to send down changes to the network access device. There's not an A-V pair for interface description that I'm aware of.
There's no official guidance or best practice recommendation that I've ever seen. It's very much a local preference whether or not to even use interface descriptions.
Personally I use them only for a quick visual check for what a given interface should be. They can be misleading though as they are only as good as your knowledge of and control over the physical connections to your devices.
That's one of the reasons we use ISE whereby the identity of what's connected to a given interface is better ascertained by looking at the Accounting record of that interface.