When I get a descent clearance, it is of the form “decent via STAR XXX to RWXX” In many cases no descent to altitude is given. This is not correct.
At TOD at least a descent to altitude must be given, if no constraints then to the end of the STAR altitude. When changing over to approach, it will give you a clearance to the initial ILS altitude where you will capture the ILS. Even when a visual approach is given, a descent altitude must be included. You are still under IFR ATC control, not flying VFR.