Definition
A prompt set is the fixed list of buyer questions a brand tracks over time. It is the denominator behind every visibility percentage, which is why changing it silently invalidates the trend it appears on.
Why it matters
Most reported improvements in AI visibility come from a changed question set rather than a changed brand. Adding easier questions raises the average without anything getting better.
How to measure it
Version the set. When you add or remove questions, either restate the history on the new set or mark the break in the trend; never compare across a silent change.