It has been established that a character cannot willingly choose to fail a saving throw. But can they willingly fail an ability check contest?
While most spells say that the target must succeed to fail a Saving Throw, Telekinesis states:
You can try to move a Huge or smaller creature. Make an ability check with your spellcasting ability contested by the creature's Strength check
I wanted to cast this on the party rogue so they could get up to the second story window to sneak in; a rich man's Levitate spell. Alternately, cast it on a fighter and help him chase around the flying monsters.
The obvious work around is to have them stand on an object that cannot contest the spell and lift them up, but then there is a chance of balance failing.
In the PHB, it talks about ability score contests:
Sometimes one character's or monster's efforts are directly opposed to another's. This can occur when both of them are trying to do the same thing and only one can succeed, such as attempting to snatch up a magic ring that has fallen on the floor. This situation also applies when one of them is trying to prevent the other one from accomplishing a goal — for example, when a monster tries to force open a door that an adventurer is holding closed. In situations like these, the outcome is determined by a special form of ability check, called a contest.
This assumes that the two efforts are at odds. However in this case a contest would not be required as the characters are working together. But the spell description bypasses that and flat out says there is a contest; no mention of willing or unwilling.
So can my warlock give a boost easily, or is there a chance of failure?