Universal Commerce Protocol (UCP)

What is the Universal Commerce Protocol (UCP)?

The Universal Commerce Protocol (UCP) is an open standard created by Google that enables AI agents to discover products, build shopping carts, and complete purchases across different merchants and surfaces. It provides a common interface between AI agents and merchant systems, allowing agents to handle the full shopping journey end-to-end while the merchant retains control as the Merchant of Record.

The Universal Shopping Aisle

Imagine walking into a grocery store where every aisle is organized by a different company with different labels, different shelf heights, and different checkout systems. Finding what you need requires knowing each company’s layout. Now imagine a universal standard: every store uses the same aisle labels, the same shelf format, and the same checkout process. You can walk into any store and shop the same way.

The Universal Commerce Protocol is that standard for AI agents. Before UCP, every merchant’s product catalog, cart system, and checkout flow was different. An AI agent trying to shop across merchants had to learn each one’s system separately. UCP gives merchants a common format so any AI agent can discover products, build a cart, and complete a purchase using the same protocol.

How UCP works

The three-step shopping journey

UCP enables AI agents to handle three stages of the shopping journey:

1. Product discovery. The agent queries a merchant’s product catalog using UCP’s standardized format. The merchant decides which products to expose and in what level of detail.
2. Cart building. The agent adds items to a cart, applies any available promotions, and prepares for checkout. The March 2026 update added full cart support as a first-class UCP capability.
3. Checkout and payment. The agent completes the purchase using the merchant’s existing payment integrations. Payment is handled through tokenization with the merchant’s payment handlers, and shoppers can use Google Pay and Google Wallet shipping/profile data to speed up the process.

Three transport bindings

UCP supports three communication methods, and merchants choose which ones to implement:

• REST API. The traditional web API approach. The agent makes HTTP requests to the merchant’s UCP endpoints.
• MCP binding. Uses Anthropic’s Model Context Protocol, allowing agents that support MCP to interact with merchant systems through the MCP tool-calling interface.
• A2A binding. Uses Google’s Agent-to-Agent protocol, enabling agent-to-agent communication between the shopping agent and merchant-side agents.

This flexibility means a merchant can start with REST and add MCP or A2A support as the ecosystem matures.

Merchant control

UCP is designed so that merchants retain full control over their commerce operations:

• The merchant decides which products to expose through UCP and at what level of detail.
• The merchant remains the Merchant of Record, meaning the merchant owns the customer relationship, handles fulfillment, and manages returns.
• The merchant chooses which UCP capabilities to support and which transport bindings to implement.
• The merchant retains ownership of customer data.

Launch and timeline

UCP was announced on January 11, 2026, at NRF 2026 (the National Retail Federation’s annual conference) by Google CEO Sundar Pichai. The initial launch included five major retail partners: Shopify, Etsy, Wayfair, Target, and Walmart [1].

At launch, UCP supported product discovery and checkout. In March 2026, Google added cart support, product catalog access, and simplified merchant onboarding, completing the full shopping journey capability [2].

Google also introduced Business Agent, a companion product that lets shoppers chat directly with brands on Google Search in the brand’s voice, powered by UCP [1].

As of mid-2026, UCP operates within Google Search AI Mode and Gemini apps for U.S.-based retailers, with 20+ merchant endorsers beyond the original five launch partners [1].

How UCP fits with other protocols

UCP is one of several protocols forming the infrastructure layer of the agentic economy. It is designed to interoperate with:

• Agent Payments Protocol (AP2). Google’s payment-side protocol for handling the financial transaction after UCP manages the shopping journey. Where UCP handles product discovery and cart building, AP2 handles the payment authorization and settlement.
• Agent-to-Agent (A2A). Google’s protocol for agent-to-agent communication. UCP’s A2A binding allows shopping agents to communicate directly with merchant-side agents.
• Model Context Protocol (MCP). Anthropic’s protocol for connecting AI agents to external tools and data. UCP’s MCP binding allows agents using MCP to interact with merchant systems through the standard MCP interface.

Together, these protocols cover different parts of the agent commerce stack: UCP for the shopping journey, AP2 for payments, A2A for agent communication, and MCP for tool integration.

Frequently asked questions

Is UCP a Google product or an open standard?

Both. Google created UCP and drives its development, but it is designed as an open standard that any merchant and any AI agent can implement. The three transport bindings (REST, MCP, A2A) mean UCP is not locked to Google’s ecosystem. Any agent that supports REST, MCP, or A2A can interact with UCP-enabled merchants.

How is UCP different from ACP (Agentic Commerce Protocol)?

ACP is an open standard co-developed by OpenAI and Stripe, launched in September 2025, focused on enabling checkout through ChatGPT and partner agents. UCP is Google’s equivalent, launched January 2026, focused on enabling AI agents to handle the full shopping journey within Google’s ecosystem and beyond. Both aim to enable agent-mediated commerce, but they come from different organizations and have different initial integrations. The ecosystem is large enough for multiple standards to coexist and interoperate.

Do merchants need to use Google’s payment system?

No. UCP uses tokenization with the merchant’s existing payment integrations. The merchant retains control of payment processing. Google Pay and Google Wallet can speed up checkout by providing shipping and profile data, but the merchant’s payment handlers process the transaction.

What does it cost merchants to implement UCP?

UCP itself is an open protocol with no licensing fee. The cost is in implementation: merchants need to expose their product catalog, cart, and checkout systems through UCP’s standardized endpoints. The March 2026 update simplified onboarding, but merchants still need engineering resources to integrate.

Key takeaways

• UCP is Google’s open standard enabling AI agents to discover products, build carts, and complete purchases across merchants.
• Announced January 11, 2026 at NRF 2026 with Shopify, Etsy, Wayfair, Target, and Walmart as launch partners.
• Supports three transport bindings (REST, MCP, A2A) so merchants can choose their integration path.
• The merchant retains control as Merchant of Record, owns customer data, and decides which products to expose.
• UCP interoperates with AP2 (payments), A2A (agent communication), and MCP (tool integration) as part of the agentic commerce infrastructure stack.

Sources

[1] Universal Commerce Protocol – Merchant Documentation, Google for Developers, January 11, 2026.

[2] Google UCP March 2026 Update: Cart Support and Product Catalog Access, Google, March 2026.