On the standard plans: per site, never pooled
Tracked prompts are counted against the site they belong to — 25 per site on Starter, 40 per site on Growth, 50 per site on Business — and are never drawn from one account-wide allowance. Adding a second brand does not take prompts away from the first, and a busy site cannot quietly starve a quiet one. The same is true of tracked competitors: 5, 15 and 20, each counted per site.
On the agency card: one allowance across the book
An agency book is the deliberate exception. Every live client site adds 50 prompts to a single allowance shared across all of your clients, and any of them can draw on it. A client with a complicated category can run 80 questions while a straightforward one runs 30, without you buying a bigger plan for the first or wasting half of one on the second.
The allowance is granted by the same rule that bills: a site contributes its 50 once it has run for the first time — the one exception being that a site you are still setting up can draw on its own 50 straight away — so the allowance always tracks what you are paying for. Prospects sit outside it in both directions. The clients screen shows what the whole book has used and how much is spare, so a client that has grown into more questions than you expected is visible rather than a surprise.