Which types of clearances allow for descent at the pilot's discretion?

Descent at the pilot's discretion is typically associated with specific clearances that provide the pilot flexibility in managing their altitude during certain phases of flight. In this context, cruise clearances grant pilots the authority to manage their descent according to their operational needs and the conditions they encounter, allowing them to descend at their discretion within the altitude assigned.

Crossing restrictions and approach clearances can also come into play, as they often allow pilots to descend in a manner that aligns with air traffic requirements while still granting a degree of operational flexibility. However, while approach clearances provide guidance on when to descend toward the airport for landing, they often include specific instructions about altitude management as the aircraft approaches.

On the other hand, VFR clearances do not inherently imply permission for descent at the pilot's discretion since they often involve adhering to visual flight rules which can include specific altitude requirements. Taxi clearances deal with ground movement and do not pertain to altitude management during flight. Thus, the combination of crossing restrictions and the nature of cruise clearances aligns best with the concept of allowing descent at the pilot's discretion, reinforcing why this answer encompasses the allowable scenarios for that situation.