Merchant Center now has a UCP integration hub, gradually rolling out in the U.S., where selected merchants choose which Universal Commerce Protocol capabilities to implement. The choice is not neutral. Cart transfer, where the shopper finishes checkout on the merchant’s own site, gets a fast-track validation path, while identity linking can only be selected together with native checkout on Google. Funnel numbers sit in an Analytics tab, and the documentation doesn’t say whether a cart handed off to a merchant site shows up there as a purchase.
What is the UCP integration hub in Merchant Center?
The UCP integration hub is a section of Merchant Center, found under Settings, where merchants select UCP capabilities, test them in a sandbox and go through validation. Google’s help page calls UCP “a new open standard for agentic commerce” and says that integrating with it lets a merchant implement a checkout button on eligible product listings in AI Mode in Google Search and on Gemini. The hub is rolling out gradually in the U.S., with Australia and Canada to follow.
Who can get in, and in what order?
Not every U.S. merchant. According to the Merchant Center Help article on onboarding, the first step is to complete the technical implementation described in the UCP developer guide, which is “necessary before you begin onboarding.” Next comes an interest form, and only selected merchants get the onboarding experience in Merchant Center.
That experience includes a sandbox for validating the UCP profile, cart transfer and native checkout APIs. Once validation is complete, the developer integration guide says the Google Support team reviews the integration and notifies the merchant whether the account is live or needs fixes. A separate Google help article describes the checkout feature as “available for select merchants at this time.” Search Engine Roundtable reported the gradual U.S. rollout on October 7.
How does the capability choice change the work?
The hub offers three capabilities, and the validation checklist adjusts to the selection:
- Transfer to merchant cart: shoppers add products to a cart on Google, then move to the merchant’s site to finish checkout, via the Cart API.
- Native checkout on Google: shoppers buy directly on Google through three core REST endpoints for session creation, updates and completion.
- Identity linking: loyalty benefits and authenticated checkouts, implemented with OAuth 2.0.
Cart transfer gets the lighter route. Google describes a “fast-track validation path” that “doesn’t require full product feed setup, product warnings, or customer support information.” The cart-only checklist asks for the matching product ID configuration and a cart transfer validation.
Native checkout carries more. Its checklist adds order status, where merchants “configure webhooks to send order updates to Google,” and a step to review and agree to the UCP Program Addendum. Identity linking has a dependency: it “becomes available for selection only if you select the Native checkout on Google option.” A merchant that wants identity linking therefore takes on native checkout too. Choosing both means completing the checklist items for both. Google’s help material adds that with native checkout the merchant remains the merchant of record.
What does the Analytics tab report, and what does it leave out?
The hub has two tabs, Overview and Analytics, and the integration guide says the Analytics tab gives visibility into the UCP checkout funnel. According to the guide’s analytics page, the dashboard requires the Performance role in Merchant Center and lists these metrics:
- Clicks to Buy, the number of times shoppers clicked the UCP “Buy” button
- Purchases, “the total number of successful transactions completed using UCP”
- Purchase Rate, the share of Clicks to Buy that resulted in a successful purchase
- Average Order Value and Cancellations
- Account Linking, where applicable, and Top Selling UCP Products
A cart transferred to a merchant’s site and paid there is a transaction, but whether it counts as “completed using UCP” isn’t answered in the pages we read. Purchase Rate is measured against Clicks to Buy, and the docs don’t say whether a cart handoff registers on either side of that ratio. Until Google says, reconcile that number against your own order data.
Why does this matter for measurement?
AI Mode is one of the surfaces where the Buy button appears, and cart transfer is the capability that sends a buyer onward to a merchant’s site. Our report on AI Mode monitoring raised the same kind of question about another feature: whether an update sends anyone to a website. For channels that do report, the picture changes. Shopify’s May admin section, covered in our piece on Agentic Storefronts becoming measurable, pulled AI sales out of “Other” buckets. The Merchant Center tab does something similar for UCP checkout, within the limits above.
Two things are worth checking after onboarding: whether the capabilities in your UCP profile exactly match the ones you selected, and whether a test order placed through cart transfer appears under Purchases. The Search Engine Roundtable post, which credits Hana Kobzová, quotes the hub’s own wording about enabling agentic actions “starting with checkout directly on Google.” That phrasing puts native checkout first. Whether cart transfer is measured the same way is the open item.