Product schema missing GTIN/MPN - reduced AI Shopping eligibility

GTIN (a Global Trade Item Number, covering UPC, EAN and ISBN formats) and MPN (Manufacturer Part Number) are standard product identifiers that let shopping platforms match your listing against external product databases. This check found your Product schema present but missing both, so there's no identifier tying your listing to the broader product catalogue these platforms use. ChatGPT Shopping and Perplexity Shopping specifically require a GTIN or MPN to match your product against external databases for price comparison and availability checks. Without one, your product can be functionally excluded from AI shopping results even if every other part of your schema is correct. Your developer needs about 1 day to add this across the catalogue. Add the appropriate GTIN field, depending on the identifier format you have, to every Product schema block, sourced from your supplier. For private-label products with no GTIN, an MPN (a manufacturer part number you assign in-house) is an acceptable substitute.