What is checked
The facts you state on the brief: prices and plans, the cities served, the founding year, integrations, whether there is a free tier. When an answer’s sentence about your brand contradicts one of them, the answer is marked with the fact and the wording the engine used.
How a session reports it
Wrong facts are folded: one wrong price stated on thirty prompts is one problem, not thirty. The session outcome carries the count, the accuracy page lists each wrong fact with the engines that stated it and how many times, and the worst engine is named.
Where wrong facts come from
Almost always from a third-party page the engine read: an old listing, a comparison written before a price change, a directory. The answer records the page it cited, so the fix is usually to correct that page or to publish the fact plainly on your own site under a heading the engine will read.
What it costs
Nothing extra. The check runs over the sentence the stance reader already found, so it adds no call to any engine.