Google Expands Universal Commerce Protocol: Cart, Catalog & Easier Onboarding Now in Play

Google has rolled out a meaningful set of upgrades to its Universal Commerce Protocol (UCP), the open shopping standard it introduced at NRF in January 2026. The latest update brings three new building blocks to the table — Cart management, Catalog access, and a simplified Merchant Center onboarding flow — signalling that Google is serious about making AI-powered checkout a mainstream reality, not just a concept.

What Is UCP and Why Does It Matter?

For those catching up: Universal Commerce Protocol is Google’s attempt to standardise how AI agents handle the entire shopping journey — from product discovery to actual purchase. Instead of a shopper having to navigate a retailer’s website manually, UCP-compatible AI agents (think Google’s AI Mode or Gemini) can do the heavy lifting — searching products, comparing options, and completing transactions on the shopper’s behalf.

The protocol launched as a checkout-focused tool. But this new update pushes it well beyond that starting point.

What’s New: Three Key Additions

Cart

The Cart capability allows AI agents to add multiple items to a shopping basket from a single store — in one go, before the shopper confirms a purchase. Until now, UCP was largely built around single-item checkout flows. With Cart, agents can help shoppers build out a full order, giving users the ability to review everything before committing. Think of it as your AI assistant filling your trolley while you supervise. Once the shopper is ready, that cart converts directly into a checkout session.

Catalog

The Catalog spec enables agents to pull live product data straight from a retailer’s inventory — including variants, pricing, and stock availability. This is a significant step forward. Earlier, agents had to lean on static product feeds, which often lagged behind actual inventory. Now, an agent querying “do you have this in blue, size M, under ₹3,000?” can get a real-time answer from the retailer’s live catalog, making product discovery far more reliable.

🔗 Speaking of AI reshaping how shoppers discover and research products — OpenAI too entered the AI shopping space with its Shopping Research Assistant inside ChatGPT, signalling that the entire industry is moving toward agent-first commerce.

Identity Linking

Already part of the stable UCP spec since launch, Google has now highlighted Identity Linking as a ready-to-use option for retailers joining the protocol. Using OAuth 2.0, shoppers can connect their retailer accounts to UCP-integrated platforms. What that means in practice: if you have a loyalty membership, a members-only discount, or free shipping entitlement with a brand, those benefits travel with you even when you’re shopping through Google’s AI Mode or Gemini — not through the retailer’s own site.

All three capabilities are optional. Retailers pick and choose what they want to support.

Merchant Center Onboarding Gets Simpler

Alongside the protocol updates, Google has also announced a streamlined onboarding path through Merchant Center. The stated goal is to bring in “more retailers of all sizes,” acknowledging that UCP’s earlier adoption required fairly heavy technical investment.

The rollout for the simplified onboarding process will happen over “the coming months.” For now, the checkout feature remains available to selected merchants, with an interest form for retailers wanting to participate. One important note: only product listings using the native_commerce product attribute will display the checkout button on Google’s surfaces.

🔗 For context on how Google has been arming businesses with more AI-powered tools overall — it’s worth reading our earlier coverage of Google’s AI-Powered Ads Advisor and Analytics Advisor, another signal of the company’s push to deeply embed AI into the merchant experience.

Platform Partners Coming On Board

Three major platforms have announced plans to implement UCP: Commerce Inc, Salesforce, and Stripe. Google says its own UCP implementations will be live “in the near future,” with others to follow.

This is good news for mid-size and smaller retailers who don’t have dedicated engineering teams. Platform-level support means you won’t necessarily need to build a custom UCP integration from scratch — your existing commerce stack may do it for you.

What This Means for Retailers

The honest answer is: it depends on how you look at it.

On one hand, Cart and Catalog capabilities mean UCP is maturing into something much closer to a full shopping experience — inside Google’s platforms. Agents can now discover products, compare in real-time, build baskets, and check out — all without the shopper ever visiting a retailer’s website. For brands that struggle with discoverability, this is a genuine opportunity to reach buyers where they already are.

On the other hand, the core tension remains unchanged. Sales happening on Google’s surfaces mean less first-party data, less control over the experience, and reduced organic traffic to owned sites. Identity Linking partially softens this by preserving loyalty perks — but retailers who use loyalty programmes as a driver of direct visits may find that trade-off less comfortable.

The Cart and Catalog specs are still in draft, meaning community feedback can still shape how they evolve. For retailers, now is the time to engage with the open-source project and push for specifications that reflect real business needs.

Opositive’s Take

From where we sit, Google’s UCP expansion is one of the more consequential moves in e-commerce this year. The shift from single-item checkout to full cart-and-catalog management marks UCP’s transition from a proof-of-concept into something retailers actually have to take seriously. Add Merchant Center’s simplified onboarding and platform support from Salesforce and Stripe, and the barrier to entry drops meaningfully — particularly for D2C brands and mid-market retailers.

The bigger picture here is that Google is effectively building an AI-first commerce layer on top of search. For SEO professionals and digital marketers, this means product visibility is increasingly going to be determined by how well your catalog integrates with UCP-compatible agents, not just how well your pages rank. Those who start experimenting now — even just with Merchant Center onboarding — will be better positioned than those who wait for the spec to finalise.

Watch this space. The coming months, as Merchant Center rollout progresses and platform partners go live, will tell us a great deal about how fast UCP adoption scales.

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