Google’s UCP Update: AI Shopping for Carts, Catalogs & Loyalty

Google’s Universal Commerce Protocol has taken a major leap forward, now supporting shopping carts, live catalog queries, and loyalty program integrations for AI-driven transactions. On March 19, Google unveiled three new UCP capabilities alongside a streamlined onboarding path through Merchant Center, arriving just two months after the initial UCP announcement with Shopify at the National Retail Federation conference in January 2026.

That January debut featured an impressive coalition including Mastercard, Visa, Walmart, Target, and Best Buy, but its practical scope was narrow. UCP could only manage single-item checkout sessions, leaving much of its potential untapped. The March update bridges the gap between UCP’s ambition and its real-world utility.

I explored UCP extensively in Selling to AI: The Complete Guide to Agentic Commerce, where I compared it to OpenAI and Stripe’s Agentic Commerce Protocol (ACP). Here’s what changed in March and what it means for retailers.

What Google Added

Cart. The new Cart capability allows AI agents to add multiple items to a shopping cart from a single retailer in one operation. Previously, UCP only supported single-item checkout sessions, meaning an agent buying three products from one store had to execute three separate transactions. Cart also enables pre-purchase exploration: agents can build baskets before a shopper commits, then convert that basket into a checkout session when the shopper is ready. UCP Cart is currently published as a draft specification.

Catalog. The Catalog capability lets agents query real-time product details directly from a retailer’s inventory, including variants, pricing, and stock levels. The key difference from existing Google Shopping product feeds: feeds are static snapshots updated periodically, while Catalog delivers live data at the moment of the query. An agent using Catalog can check whether a specific size is in stock before showing the product to a shopper. UCP Catalog is also a draft specification.

Identity Linking. The Identity Linking capability enables shoppers to connect retailer accounts to UCP-integrated platforms using OAuth 2.0. When a Nike member buys through Google AI Mode, Identity Linking carries over their member pricing, discounts, and free shipping. Without it, shopping through an AI agent means losing the loyalty benefits they would get when logged into the retailer’s website directly. Identity Linking is the only capability in this update that is already part of UCP’s stable release, not a draft.

Simplified Onboarding

Google is building a simplified UCP onboarding process directly into Merchant Center, targeting retailers who lack engineering teams for implementing a protocol from scratch. Google says the Merchant Center UCP rollout will happen “over the coming months.”

One concrete detail: products using the native_commerce product attribute will display a checkout button in Google AI Mode and the Gemini app. For retailers already managing product feeds through Google Merchant Center, UCP onboarding should be a settings change rather than an integration project.

Platform Partners

Commerce Inc, Salesforce, and Stripe will implement UCP on their platforms, with Google describing the timeline as “in the near future.” Retailers on these platforms won’t need to implement UCP directly. The platform handles the protocol layer, similar to how Shopify’s Agentic Storefronts already abstract away multi-protocol complexity for Shopify merchants.

Salesforce’s dual-protocol position is noteworthy. Salesforce announced ACP support in October 2025. With UCP support coming too, Salesforce Commerce Cloud merchants will be able to serve both protocols from a single platform, reaching AI agents on ChatGPT (via ACP) and Google AI Mode (via UCP) without separate integrations.

Stripe occupies an even more central role. Stripe co-created ACP with OpenAI and is now implementing UCP as well. Stripe is becoming the shared payment layer across both competing agentic commerce protocols.

What This Means

UCP’s January announcement was a statement of intent. UCP’s March update is a statement of readiness. Three things stand out:

UCP is reaching feature parity with ACP. OpenAI and Stripe’s Agentic Commerce Protocol launched in September 2025 with cart management and catalog access built in from day one. UCP launched in January 2026 without either. Cart, Catalog, and Identity Linking close that gap, giving UCP the core primitives AI shopping agents need for multi-item, loyalty-aware transactions.

Google’s onboarding play targets mass adoption, not enterprise showcases. Google wants millions of Merchant Center retailers on UCP, not just the enterprise brands that endorsed UCP at NRF. Merchant Center integration is how Google reaches that scale. A retailer managing Google Shopping feeds today could become UCP-enabled without writing a line of code.

Identity Linking is UCP’s clearest differentiator over ACP. Neither ACP nor any other agentic commerce protocol offers an equivalent. Identity Linking solves a specific adoption barrier: shoppers lose loyalty pricing, member discounts, and free shipping when buying through an AI agent instead of logging into a retailer’s website directly. Removing that friction makes agentic commerce more attractive to both retailers protecting their loyalty programs and shoppers unwilling to give up membership benefits.

For businesses already thinking about agentic commerce, the action items remain the same: clean product data, structured markup, and being on a platform that handles protocol complexity. What changed in March is that UCP is no longer a specification to watch. Google is building UCP into the infrastructure retailers already use.