14 CFR 61.95 requires solo student pilots to have an endorsement to (a) fly through class B airspace or (b) takeoff/land at a class B airport. However, the requirements to get it are pretty vague:
(1) The student pilot has received both ground and flight training from an authorized instructor on that Class B airspace area, and the flight training was received in the specific Class B airspace area for which solo flight is authorized;
There are similarly vague training requirements for Recreational pilots in 14 CFR 61.101(d) and Sport pilots in 14 CFR 61.325.
Is any particular content or amount of time expected, or is it at the CFI's sole discretion to decide when a given pilot is competent enough to endorse? Does the training itself need to be logged as such, separate from the endorsement?