If one departed with flight plan fuel and diverted to the alternate then final reserve+contingency is the required amount of fuel one should have upon touch down at the alternate. If things didn't work out as planned then it's only final reserve. So what's the problem? There's a call such as minimum fuel before one screams MAY DAY or even PAN PAN PAN.
MINIMUM FUEL
The term used to describe a situation in which an aircraft’s fuel supply has reached a state where little or no delay can be accepted.
NOTE: This is not an emergency situation but merely indicates that an emergency situation is possible, should any undue delay occur.
No harm in advising ATC of a min fuel as a heads up.
