Why these facts are different
A product's GTIN never changes; its price may change several times a week, and differs by seller and country. A model that read a page in August and answers in September repeats the August price with the confidence of a September fact — unless the page said when the price was observed.
How to publish offers
- Date every offer. "USD 129, observed 21.09.2026" is a fact about a moment;
"USD 129" is a claim about now.
- Keep offers separate from identity. A price is an observation about a
seller, not a property of the product. Our records publish them on a separate surface for this reason.
- Name the seller and the market. One product can have several prices at
once, all correct.
What not to expect
That an answer will always carry today's price. Retrieval happens when a question is asked, but the page retrieved may be a cached copy. What you can ensure is that anyone checking can see which price was true when — and the record behind it, at /products, shows offers as time-stamped observations. The evidence rules are at /evidence.