Google’s Universal Commerce Protocol can now manage shopping carts, live catalog inquiries, and loyalty program benefits with AI agent functions. On March 19, Google announced three UCP capabilities and a simplified onboarding process through Merchant Center, two months after Google and Shopify introduced UCP at the National Retail Federation conference in January 2026.
The January launch had a major alliance (Mastercard, Visa, Walmart, Target, Best Buy) but limited performance. UCP can handle single transaction payment sessions and not much else. The March update closes the gap between UCP’s aspiration and UCP’s practical capability.
I covered UCP in depth in Marketing AI: The Complete Guide to Agentic Commerce, where I compared UCP to OpenAI and Stripe’s Agetic Commerce Protocol (ACP). This article covers what changed in March and what the changes mean for retailers.
Added by Google
A carriage. The new UCP Cart capability allows AI agents to add multiple items to a shopping cart from a single merchant in a single operation. Until March 2026, UCP only supported single-item checkout sessions, meaning an agent buying three products from one store needed three separate transactions. Cart capabilities also support pre-purchase testing: agents can create baskets before a shopper takes action, then convert the basket into a checkout session when the shopper is ready. UCP Cart is currently published as a draft specification.
Catalogue. New UCP catalog capabilities allow agents to query real-time product information directly from a vendor’s inventory, including variants, prices, and stock levels. The difference between the Catalog and the feed of existing Google products: the product feed is a dynamic snapshot that is updated periodically, while the Catalog provides live data at the time of the query. An agent using the Catalog can check if a particular size is still in stock before presenting the product to the buyer. The UCP catalog is also an incomplete description.
Identity Linking. UCP’s Identity Linking capabilities allow consumers to link merchant accounts to UCP’s integrated platforms using OAuth 2.0. When a shopper with a Nike membership makes a purchase through Google AI Mode, Identity Linking carries that shopper’s prices, discounts, and free shipping. Without Identity Linking, shopping with an AI agent means losing the loyalty benefits a buyer can get when logging in to the seller’s website directly. Identity Linking is the only capability in this update that is already in the stable release of UCP rather than the draft.
Riding Made Easy
Google is building a simplified UCP onboarding process directly into the Merchant Center, which guides merchants without development teams to implement the protocol from scratch. Google says the rollout of Merchant Center UCP will happen “in the coming months.”
One obvious detail: products that use i traditional_trade product feature will show payment button in Google AI Mode and Gemini app. For merchants who already manage product offerings through Google Merchant Center, onboarding UCP should be a configuration change rather than an integration project.
Platform Partners
Commerce Inc, Salesforce, and Stripe will use UCP on social media, with Google describing the timeline as “in the near future.” Merchants on Commerce Inc, Salesforce, or Stripe will not need to use UCP directly. The platform hosts a protocol layer, similar to how Shopify’s Agetic Stores are already invisible from the complex process of protocols for Shopify merchants.
Salesforce’s dual-protocol position is notable. Salesforce announced support for ACP in October 2025. With UCP support also coming, Salesforce Commerce Cloud vendors will be able to offer both deals from a single platform, accessing AI agents in ChatGPT (via ACP) and Google AI Mode (via UCP) without separate integrations.
Stripe takes an even more central position. Stripe was jointly developed by ACP and OpenAI and now uses UCP as well. Stripe is becoming a shared payment layer for both competing commercial protocols.
What does this mean
The UCP’s January announcement was a statement of intent. The March update of the UCP is a statement of preparedness. Three things stand out:
UCP achieves feature parity with ACP. OpenAI and Stripe’s Agetic Commerce Protocol launched in September 2025 with cart management and catalog access built in from day one. The UCP was launched in January 2026 without any qualification. Cart, Catalog, and Ownership Bridging that gap, provides UCP with the primary tools retail agents need to manage multiple, loyalty-aware transactions.
Google’s onboarding play is aimed at mass adoption, not business shows. Google wants millions of Merchant Center merchants in the UCP, not just the business brands (Walmart, Target, Best Buy) that have approved the UCP in the NRF. Merchant Center Integration is how Google achieves that scale. A merchant running Google Shopping feeds today can be enabled for UCP without writing a line of code.
Identity Linking is a clear difference of UCP from ACP. Neither ACP nor any other commercial protocol provides an equivalent to Identity Linking. Identity Linking solves a particular barrier to adoption: shoppers miss out on loyalty rates, member discounts, and free shipping when shopping with an AI agent instead of going directly to the retailer’s website. Removing that friction makes commerce more attractive to both merchants who protect their loyalty programs and consumers who aren’t willing to give up membership benefits.
For businesses that are already thinking about agent trade, the action items remain the same: clean product data, structured markups, and being on a platform that handles protocol complexity. What has changed in March is that UCP is no longer something to watch. Google builds UCP for infrastructure vendors that already use it.
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This post was originally published on No Hacks.
Featured Image: Inkoly/Shutterstock
