Eureka! I’ve been wrestling with the way I’ve written my contest mechanics for Hari Ragat for some time now. I think I have it.
The most basic structure of a contest is to declare actions, roll, compare to find the winner, and narrate the results.
But there are also many contests where you don't want to just give up if you lose the roll. Specially if it means your character got killed. So to continue the contest, you have to pay a cost.
Basically it's like feeding coins into an arcade machine. Game over? Not yet, not as long as you have coins and are willing to spend them. As long as you can pay the cost to continue, you can continue the contest, or try to negotiate, or try to turn the contest into another kind of contest where you're more likely to win.
Different resources can be used to pay the continue cost for different types of contests. Say you lose an exchange in lethal combat. Rather than let your character die, you pay points from your shield or armor, trading the usable life of those items for another chance to be the victor. Say you lose an attempt to resist a diwata's seduction. Rather than let your character do as the diwata wishes, you pay points from your willpower.
The GM's characters also have similar resources. The more important the character, the greater these resources, so contests against them will be harder to win.