Google’s Universal Commerce Protocol can now handle shopping carts, live catalog queries, and loyalty program benefits for AI agent transactions. On March 19, Google announced three new UCP features and a simplified integration journey via Merchant Center, two months after Google and Shopify unveiled the PCU at the National Retail Federation conference in January 2026.
The January launch had a large coalition (Mastercard, Visa, Walmart, Target, Best Buy) but limited functionality. UCP could handle single-item checkout sessions and not much else. The March update closes the gap between the UCP’s ambition and its practical capacity.
I covered UCP in depth in Selling to AI: the complete guide to agent commercewhere I compared UCP to OpenAI and Stripe Agent Commerce Protocol (ACP). This article covers what changed in March and what these changes mean for retailers.
What Google added
Cart. UCP’s new Shopping Cart feature allows AI agents to add multiple items to a shopping cart from a single retailer in a single transaction. Until March 2026, UCP was only supported single item checkout sessionsmeaning that an agent purchasing three products from a store had to complete three separate transactions. The Cart feature also supports pre-purchase exploration: agents can create carts before a buyer commits, then convert the cart to a checkout session when the buyer is ready. UCP Cart is currently released as a draft specification.
Catalog. UCP’s new Catalog functionality allows agents to query product details in real time directly from a retailer’s inventory, including variants, prices and stock levels. The difference between Catalog and existing Google Shopping product feeds: Product feeds are static snapshots that are updated periodically, while Catalog provides live data at query time. An agent using Catalog can check if a specific size is in stock before presenting the product to a buyer. The UCP catalog is also a draft specification.
Identity link. UCP’s Identity Linking feature allows buyers to connect retailer accounts to UCP-integrated platforms using OAuth 2.0. When a buyer with a Nike membership purchases through Google AI Mode, Identity Linking reports prices, discounts, and free shipping from that buyer’s member. Without Identity Linking, shopping through an AI agent means losing the loyalty benefits a shopper would enjoy if connected directly to the retailer’s website. Identity Binding is the only feature in this update already present in the stable version of UCP rather than the preview version.
Simplified integration
Google is building a streamlined UCP onboarding process directly into Merchant Center, targeting retailers who don’t have engineering teams to implement a protocol from scratch. Google says the Merchant Center UCP rollout will take place “over the coming months.”
A concrete detail: products using native_commerce The product attribute will display a payment button in Google AI mode and in the Gemini app. For retailers who already manage their product feeds through Google Merchant Center, integrating UCP 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 Commerce Inc, Salesforce or Stripe will not need to implement UCP directly. The platform manages the protocol layer, similar to how Shopify’s agent storefronts already eliminate multi-protocol complexity for Shopify merchants.
Salesforce’s position on dual protocols is remarkable. Sales force announced ACP support in October 2025. With UCP support also coming, Salesforce Commerce Cloud merchants will be able to serve both protocols from a single platformreaching AI agents on ChatGPT (via ACP) and Google AI Mode (via UCP) without separate integrations.
Stripe occupies an even more central position. Band co-created ACP with OpenAI and now also implements UCP. Stripe becomes the shared payment layer between the two competing agent commerce protocols.
What this means
The UCP’s January announcement was a statement of intent. The UCP’s March update is a statement of preparedness. Three things stand out:
UCP achieves feature parity with ACP. OpenAI and Stripe’s Agentic Commerce Protocol launched in September 2025 with shopping cart management and catalog access built in from day one. UCP launched in January 2026 without any of these capabilities. Shopping cart, catalog, and identity linking bridge this gap, giving UCP the core primitives that AI purchasing agents need to manage multi-item and loyalty-conscious transactions.
Google’s onboarding game is aimed at mass adoption, not enterprise storefronts. Google wants millions of Merchant Center retailers to use UCP, not just enterprise brands (Walmart, Target, Best Buy) that have approved UCP at NRF. Merchant Center integration allows Google to achieve this scale. A retailer running Google Shopping feeds today could become UCP compliant without writing a single line of code.
Identity Linking is the most obvious differentiator of UCP versus ACP. Neither ACP nor any other agent commerce protocol offers an equivalent to Identity Linking. Identity Linking addresses a specific adoption barrier: Shoppers lose loyalty pricing, member discounts, and free shipping when they purchase through an AI agent instead of connecting directly to a retailer’s website. Removing these frictions makes agent commerce more attractive both to retailers protecting their loyalty programs and to shoppers unwilling to give up membership benefits.
For companies that are already thinking trade agentthe 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 spec to watch. Google integrates UCP into the infrastructure that retailers already use.
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This article was originally published on No hacks.
Featured image: Inkoly/Shutterstock
