How to fix it
- Populate the barcode field on each variant in Shopify. It maps to gtin in structured data and to the identifier Google Merchant Center wants.
- Set a real vendor per product rather than reusing the store name for everything.
- If you manufacture the product, assign your own MPN and keep it stable across seasons.
Why an agent cares
Comparison is the core of what a shopping agent does. To compare, it first has to match: to know that your listing and four others all refer to one item, so that price, shipping and stock can be set against each other.
Matching on title alone is unreliable, because every retailer writes the title differently. A GTIN makes the match certain. Without one, you are either excluded from the comparison or matched by fuzzy text, which can attach your price to the wrong product.
For own-brand goods with no GTIN, brand plus MPN does the same job. The failure case is having neither, which leaves nothing to match on.
Check your own store
This check runs as part of a full audit, alongside 18 others. Nothing to install.
Other structure checks
Missing Product structured dataWithout Product or ProductGroup JSON-LD, price and stock have to be inferred from your layout rather than read.Ratings not exposed to machinesReviews rendered only as pixels cannot be read by an agent ranking options on quality.Price or availability missing from structured dataA Product block with no complete offer tells an agent the page exists but not whether it can be bought.