Google updated the Universal Commerce Protocol with new Cart and Catalog capabilities, highlighted Identity Linking as an available option, and announced a simpler onboarding process through Merchant Center.
The update is UCP’s first since Google launched the protocol at NRF in January. Cart and Catalog are published as draft specifications. Identity Linking is in the latest stable version of the spec.
What The New Capabilities Do
The additions expand what AI agents can do within UCP-powered shopping experiences.
Cart lets agents save or add multiple items to a shopping basket from a single store. According to the UCP spec, Cart is designed for pre-purchase exploration, allowing agents to build baskets before a shopper commits to a purchase. Carts can then convert to checkout sessions when the shopper is ready.
Catalog enables agents to retrieve real-time product details from a retailer’s inventory. That includes variants, pricing, and stock availability. The Catalog spec supports both search and direct product lookups.
This is relevant to the product discovery question raised in earlier UCP coverage. Agents can now query live catalog data rather than relying solely on product feeds.
Identity Linking allows shoppers to connect their retailer accounts to UCP-integrated platforms using OAuth 2.0. That means loyalty pricing, member discounts, or free shipping offers can carry over when a shopper buys through AI Mode or Gemini instead of the retailer’s own site.
Identity Linking was part of the UCP spec at launch. Google’s blog post groups it with Cart and Catalog as a newly available option for adopters.
All three capabilities are optional. Retailers choose which ones to support.
Merchant Center Onboarding
Separately, Google said it is simplifying UCP onboarding through Merchant Center. The company described the process as designed to bring in “more retailers of all sizes” and said it would roll out over the coming months.
Google’s Merchant Center help page still lists the checkout feature as available to selected merchants, with an interest form for those who want to participate. The page specifies that only product listings using the native_commerce product attribute will display the checkout button.
Three platform partners announced plans to implement UCP. Commerce Inc, Salesforce, and Stripe each published separate announcements. Google said its implementations will arrive “in the near future,” with others to follow.
For retailers not building a direct UCP integration, platform support from these providers could lower the technical barrier to participation.
Why This Matters
Simplified Merchant Center onboarding and third-party platform support open the door for retailers without engineering teams building custom integrations.
Cart and Catalog also change the scope of what UCP handles. At launch, UCP could process a single-item checkout. Now agents can build multi-item baskets and pull live product data. That moves UCP closer to replicating a full shopping experience inside Google’s AI surfaces.
The tradeoffs for retailers are the same ones identified in January. Sales happen on Google’s surfaces instead of owned sites. Identity Linking adds loyalty benefits to that equation, which may make the tradeoff more palatable for some retailers and more concerning for others who see loyalty programs as a reason shoppers come to their sites directly.
Looking Ahead
Cart and Catalog are draft specifications, meaning their status may change as community contributors provide feedback in the open-source project.
Google said it plans to bring UCP capabilities to AI Mode in Search, the Gemini app, and beyond. The company has not provided a more specific timeline for the Merchant Center onboarding rollout beyond “coming months.”
