Google Adds Cart & Catalog to UCP — AI Agent Shopping Experience Goes Full-Scale

Google Adds Core Shopping Capabilities to UCP

Universal Commerce Protocol updates improve AI shopping for everyone

Universal Commerce Protocol (UCP) releases new capabilities, and Google shares a vision for a connected commerce ecosystem powered by AI.

On March 19, 2026, Google announced a major update to the Universal Commerce Protocol (UCP). According to VP/GM Ashish Gupta's official blog post, three new optional capabilities have been added: Cart, Catalog, and Identity Linking.

UCP is an open standard protocol announced at the NRF (National Retail Federation) annual conference in January 2026. It was designed as a common standard for AI agents to securely connect with retailers' systems and make purchases on behalf of users. With this update, UCP's scope has expanded significantly from checkout-only functionality to cover the entire purchasing process.

Industry Landscape

UCP's feature expansion reflects the rapid shift of the agentic commerce market into the implementation phase. According to Stripe, approximately 75% of participants at NRF 2026 sessions reported that they were either "implementing" or "planning" agentic commerce adoption. The retail industry's focus has completely shifted from "whether to adopt" to "how to implement."

As the market matures, competition between protocols is intensifying. Stripe is advancing the Agentic Commerce Protocol (ACP), onboarding major brands including URBN (Anthropologie, Free People, Urban Outfitters), Etsy, and Coach. Meanwhile, Google's UCP update aims to establish a standard covering the entire purchase journey -- from product discovery to cart building to checkout -- not just the final transaction.

Importantly, the two protocols are not mutually exclusive. Stripe has explicitly stated that its Agentic Commerce Suite "automatically supports UCP," meaning merchants can support multiple protocols through a single integration.

Cart, Catalog, and Identity Linking Explained

Cart -- Enabling Pre-Checkout Exploration

The Cart capability allows AI agents to add, update, and remove products from a cart on behalf of users. Previously, UCP only defined checkout (purchase confirmation) operations. With Cart, AI agents can now replicate the everyday shopping behavior of "adding items to the cart to consider later."

Technically, a staged purchase flow of Cart, Checkout, and Order has been defined. Cart sessions support four CRUD operations -- Create, Get, Update, and Cancel -- with support for session expiration and handoff via shared URLs (continue_url).

Catalog -- Real-Time Product Information Retrieval

The Catalog capability enables AI agents to search and browse retailers' product catalogs in real time. It supports use cases including free-text search, category and filter-based browsing, variant retrieval (size, color, etc.), and price comparison.

Notably, Catalog API responses are "session-specific," returning inventory and pricing as real-time data at the moment of the request. This ensures AI agents present users only with products that are available to purchase right now.

Identity Linking -- Cross-Platform Loyalty Benefits

Built on existing standard specifications, Identity Linking enables shoppers to carry over retailers' loyalty programs and membership benefits when shopping on UCP-enabled platforms. Specifically, benefits such as member-exclusive pricing and free shipping are applied even when purchasing through Google AI Mode or the Gemini app.

Impact and Action Items for E-Commerce Merchants

A New Sales Channel

Alongside this update, Google announced it will roll out a simplified onboarding process through Merchant Center over the coming months. This makes it easier for small and mid-sized merchants to participate in agentic commerce through Google AI Mode in Search and the Gemini app.

Expanding Partner Ecosystem

Major platform providers are also advancing UCP support. Salesforce announced it will provide native UCP support for Agentforce Commerce merchants. Commerce Inc and Stripe have also committed to UCP implementation in the near future. Merchants using existing commerce platforms may be able to join the UCP ecosystem automatically as their platform adds support.

Practical Considerations

Merchants preparing for UCP adoption should focus on the following:

• Product data quality: The Catalog capability returns real-time inventory, pricing, and variant information, meaning product master data accuracy directly impacts revenue
• Loyalty program API readiness: Leveraging Identity Linking requires exposing membership benefit logic via APIs
• Phased rollout: URBN's approach of prioritizing popular categories first has been reported as a proven strategy

Summary

With the addition of Cart, Catalog, and Identity Linking, UCP has evolved from a "checkout-only protocol" to a "commerce standard covering the entire purchase journey." With major platforms like Salesforce and Stripe announcing UCP support, the barriers to adoption are steadily decreasing.

The next steps for e-commerce merchants are to monitor the rollout of Merchant Center's simplified onboarding, while simultaneously advancing product data structuring and loyalty program API readiness. Now that AI agent-powered purchasing has entered the "how to prepare" phase rather than "when will it arrive," early preparation provides a competitive advantage.