Umezawa's Jitte is used very sub-optimally by the AI,
I don't know how the code works, but the algorithm should be:
1) Is my Jitte going to be destroyed by something on the stack?
If yes, gain life, else -
2) Is the equipped creature attacking?
2.1 If yes, is it unblocked?
2.1.1 If yes, can I boost it to kill the opponent?
2.1.2 If yes, boost creature.
2.2 (blocked) can I kill the blocking creature or prevent the equipped creature by boosting?
2.2.1 If yes, boost creature
3) Is the equipped creature blocking?
3.1 Can I prevent losing by gaining life? if yes, gain life.
3.2 Can I kill the attacking creature or prevent the equipped creature by boosting? if yes, boost
4) Is the equipped creature about to die due to damage?
4.1 If yes, can I prevent it from being killed by boosting? if yes, boost.
5) is there a threatening (this might have to be defined more accurately) creature that I can kill?
5.1 if yes, kill the creature.
6) Else just let the counters accumulate.