For some products across multiple eBay categories, eBay will have a pre-defined definition for that product in the eBay product catalog. A seller can take this catalog product data and use it to pre-fill some of the details in their listings. If a seller is able to match a book to an eBay catalog product using the book's ISBN value, the item listing will automatically pick up that catalog product's title, description, item specifics, and any stock photos that are available for the book
You can use the findItemsByProduct call to search for items that contain data matching a specified product. This call requires a product ID and the ID type. The Finding API supports the following product ID types:
ReferenceID. A global reference ID for an eBay catalog product.
ISBN. The 10 or 13-digit International Standard Book Number.
UPC. The Universal Product Code, a numeric value associated with barcodes.
EAN. The European Article Number, a numeric value associated with barcodes.
If you do not know the product ID, use FindProducts in the Shopping API to retrieve a list of catalog products. Obtain the product ID from one of these products and use it as input to findItemsByProduct to find all items that were listed based on that product.