What can Google actually read on your product page?
Paste one product URL. This reports the structured data on it — the markup that puts a price, a stock state and a rating next to your result, and that an assistant reads when somebody asks it where to buy something. Free, no sign-up, nothing stored.
What this checks, and what it does not
It reads the JSON-LD, microdata and RDFa on the page as delivered — the same HTML a crawler is given, before any JavaScript runs. It reports whether the thing for sale is declared at all, and whether the fields a product result is built from are present: a name, an image, a price with its currency, a stock state, and the identifiers that let a shopping surface group your product with the same product elsewhere.
It does not suggest you add a rating. Marking up a rating you do not have is the quickest route to a manual action, and no tool should nudge anybody towards it.
It fetches the page once, from our server, and keeps nothing: no URL is logged, no report is stored, and there is no account to make.