Yes or No answers a closed question — one with exactly two outcomes. It is good when the decision has already formed and you need the last doubt removed: file the papers today or not, message first or not, accept the meeting or not. One card gives you no analysis of the situation, but it also doesn't let you drift into rumination.
It works badly where the question is actually open. "Will I get married" is not a closed question, it is anxiety wearing a yes-no costume, and the answer changes nothing. If you want to ask "but why" straight after the answer, the question wasn't for this spread — take the situation or the relationship reading instead.

