Product data
When the scan recognizes a Shopify store, it reads the store's own public product data for up to 30 product pages in the sample and checks whether the Product structured data lists every version a shopper can buy, keeps each version's SKU and barcode on its own offer, and carries the full description. The scan also compares the price and availability in the structured data with what the page shows.
In the Shopify app: The Visibility Mesh app lists material, care and size guide facts that your product descriptions do not state, and quotes the words it found.