Back in March 2026 Google said they were going to let merchants upload customer loyalty data via the GMC API and now it's officially in the documentation.

"Customer Match via Merchant API: You can upload your customer loyalty data, such as user identifiers and loyalty tiers, to *enable personalized experiences on free listings* via Merchant API."

The help doc also has multiple examples of what the "personalized experiences" can look like on both paid and free listings, which is what I was curious about. Basically there are highlighted lower prices/free shipping offers for members visible.