You do not need to be precise, technical or organised. You need to say what the thing is, who it is for, and how money moves. Everything else we ask you.
One paragraph is plenty. Skip structure, skip jargon, skip feature lists. If you can explain it to a friend over coffee, that version is the right input.
The read-back screen shows the four things we inferred — product type, primary user, money model and key action — plus every assumption we made. Correct anything wrong there, before it hardens into decisions.
If your paragraph contains "and also", split it. Two products planned separately are far cheaper than one product that argues with itself. You can always merge later; untangling a mixed blueprint is the expensive direction.