Google’s Universal Commerce Protocol can now process 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 onboarding path through Merchant Center, two months after Google and Shopify introduced UCP at the National Retail Federation conference in January 2026.
When it launched in January, there was a large coalition (Mastercard, Visa, Walmart, Target, Best Buy) but limited functionality. UCP could handle individual checkout sessions and not much else. The March update closes the gap between UCP’s ambitions and UCP’s practical capabilities.
I covered UCP in detail in Selling to AI: The Complete Guide to Agentic Commerce, where I compared UCP to OpenAI and Stripe’s Agentic Commerce Protocol (ACP). In this article, you’ll learn what changed in March and what the changes mean for retailers.
What Google added
Shopping cart. UCP’s new shopping cart feature allows AI agents to add multiple items from a single retailer to a shopping cart in one operation. Until March 2026, UCP only supported single-item checkout sessions, meaning an agent purchasing three products in one store would require three separate transactions. The shopping cart feature also supports pre-purchase exploration: Agents can create shopping carts before a buyer commits, and then convert the cart into a checkout session when the buyer is ready. UCP Cart is currently published as a draft specification.
Catalog. UCP’s new catalog feature allows agents to query product details in real-time directly from a retailer’s inventory, including variants, prices and inventory levels. The difference between Catalog and existing Google Shopping product feeds: Product feeds are static snapshots that are updated regularly, while Catalog provides live data at the time of query. An agent using the catalog can check whether a particular size is in stock before presenting the product to a buyer. The UCP catalog is also a draft specification.
Identity linkage. UCP’s Identity Linking feature allows buyers to connect retailer accounts to UCP-integrated platforms using OAuth 2.0. When a shopper with a Nike membership purchases through Google AI mode, Identity Linking covers that shopper’s membership pricing, discounts, and free shipping. Without identity linking, purchasing through an AI agent means the shopper loses the loyalty benefits they would receive by logging in directly to the retailer’s website. Identity Linking is the only feature in this update that is already in the stable version of UCP and not in the draft.
Simplified onboarding
Google is building a simplified UCP onboarding process directly in Merchant Center, aimed at retailers who don’t have development teams to implement a protocol from scratch. According to Google, the launch of Merchant Center UCP will take place “in the coming months.”
A concrete detail: products that use this native_commerce The product attribute displays a checkout button in Google AI mode and Gemini app. For retailers who already manage product feeds through Google Merchant Center, UCP onboarding should be more of a mindset change than an integration project.
Platform partner
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 do not need to implement UCP directly. The platform manages the protocol layer, similar to how Shopify’s Agentic Storefronts already abstract the complexity of multiple protocols for Shopify merchants.
What’s notable is Salesforce’s dual-protocol position. Salesforce announced ACP support in October 2025. With the introduction of UCP support, Salesforce Commerce Cloud merchants can serve both protocols from a single platform and reach AI agents on ChatGPT (via ACP) and Google AI Mode (via UCP) without separate integrations.
Stripe takes an even more central position. Stripe developed ACP together with OpenAI and is now also implementing UCP. Stripe will become the common payment layer for both competing agent commerce protocols.
What that means
The UCP’s announcement in January was a statement of intent. UCP’s March update is a statement of preparedness. Three things stand out:
UCP achieves functional equality with ACP. OpenAI and Stripe’s Agentic Commerce Protocol launched in September 2025 with integrated shopping cart management and catalog access from day one. UCP launched in January 2026 without either feature. Shopping Cart, Catalog, and Identity Linking bridge this gap and give UCP the core foundational capabilities AI shopping agents need to handle multi-item transactions and loyalty awareness.
Google’s onboarding game is aimed at mass adoption, not corporate presentation. Google wants millions of Merchant Center merchants to use UCP, not just the corporate brands (Walmart, Target, Best Buy) that recommended UCP at NRF. Through the Merchant Center integration, Google achieves this scale. A retailer managing Google Shopping feeds today could become UCP-enabled without writing a line of code.
Identity linking is the clearest differentiating feature of UCP over ACP. Neither ACP nor any other agent commerce protocol provides an equivalent to identity linking. Identity linking solves a specific barrier to adoption: shoppers lose loyalty pricing, member discounts, and free shipping when they purchase through an AI agent instead of logging in directly to a retailer’s website. Removing these friction points makes agent trading more attractive to both retailers who protect their loyalty programs and shoppers who don’t want to miss out on membership benefits.
For companies already considering agent commerce, the action points remain the same: clean product data, structured markup, and leveraging a platform that handles protocol complexity. What changed in March is that UCP is no longer a spec to keep an eye on. Google is building UCP into the infrastructure retailers already use.
Additional resources:
This post was originally published on No Hacks.
Featured image: Inkoly/Shutterstock
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