Tinybones’s first ability triggers only if an opponent has discarded a card before the end step begins. If an opponent has more cards in hand than their maximum hand size, they’ll discard during their cleanup step, which is after the end step.

Tinybones’s first ability has you draw just one card and lose just 1 life, no matter how many opponents discarded cards and no matter how many cards were discarded beyond the first.

Tinybones checks which opponents have no cards in hand only as its last ability resolves.