Glossary
Agentic commerce glossary.
The terms of agentic commerce, defined briefly and without jargon. A stabilized vocabulary to talk about agents, protocols and payments the same way, everywhere.
Agentic commerce
Transactions where an AI agent discovers, negotiates and completes a purchase on behalf of a human, with consent. See the agentic commerce page.
AI agent
Autonomous software able to execute tasks, make decisions and interact with other systems to reach a goal set by a human.
Conversational commerce
Commerce assisted by an agent that converses and guides, but does not execute the transaction. Distinct from agentic commerce, which goes all the way to payment.
MCP (Model Context Protocol)
Open standard from Anthropic (November 2024) that connects AI agents to external tools, data and APIs. The tool-access layer.
A2A (Agent2Agent)
Open protocol from Google (April 2025) letting agents from different vendors communicate, delegate tasks and collaborate; transferred to the Linux Foundation. The agent-to-agent layer.
ACP (Agentic Commerce Protocol)
Open standard from OpenAI and Stripe (September 2025) for programmatic purchases between buyers, agents and merchants. It powered Instant Checkout in ChatGPT; OpenAI scaled back that native checkout in 2026 and now relies on Visa for payment.
AP2 (Agent Payments Protocol)
Open protocol from Google (September 2025) to authorize agent-initiated payments via cryptographic mandates. Stewarded by the FIDO Alliance; 120+ partners in 2026. The payment layer. See the AP2 page.
UCP (Universal Commerce Protocol)
Open standard from Google and Shopify (NRF, January 2026) for agentic commerce across the shopping journey. See the UCP protocol page.
Universal Cart
Multi-retailer cart powered by UCP, expanded at Google Marketing Live (May 2026): shoppers save products from several merchants and complete the purchase via Google Pay or the retailer's checkout. Rolled out in the United States first, then opened to Australia (first Asia-Pacific market) in June 2026.
/.well-known/ucp
UCP's discovery manifest: a JSON document published by the merchant at this standardized address, declaring services, capabilities and payment handlers. Agents read it to dynamically discover what the merchant supports.
Capability (UCP)
A functional commerce building block exposed by a UCP merchant: checkout, discounts, fulfillment, identity linking, order management. Capabilities are extensible and versioned.
Payment handler
In UCP, the component that processes a payment (Google Pay, Shop Pay...), distinct from the instrument the buyer uses. This separation enables compatibility with diverse payment providers.
x402
An AP2-linked extension, backed by Coinbase, for machine-to-machine stablecoin settlement. The settlement layer.
Visa Intelligent Commerce
Visa's portfolio (April 2025) connecting AI agents to the card network: agent identity, tokenized credentials, scoped authorizations. Integrated into OpenAI experiences since June 2026. See Visa and Mastercard.
Mastercard Agent Pay
Mastercard's program (2025) for agent-initiated payments, extended in June 2026 by Agent Pay for Machines (AP4M) for agent-to-agent transactions. See Visa and Mastercard.
Trusted Agent Protocol
Visa's framework to verify and govern paying agents, aligned with OpenAI's protocol as part of the June 2026 partnership.
Agent Score (Visa)
A Visa tool (June 2026) that evaluates a merchant's site for agentic commerce readiness.
Adyen Agentic
Adyen's offering (June 2026) positioned as a "universal translator" so a business can transact across the different AI commerce platforms.
Mandate (AP2)
A cryptographically signed digital proof of a user's intent. AP2 defines three: intent mandate, cart mandate, payment mandate.
Shared payment token
A single-use, time- and amount-limited payment credential passed by the agent to the merchant without exposing real credentials (ACP mechanism via Stripe).
Seller of record
The entity legally responsible for the sale. In most agentic models (UCP, ACP) the merchant remains the seller of record; the agent is only an intermediary.
Agentic checkout
The order validation and payment process triggered by an AI agent, structured by a protocol such as UCP or ACP.
Product feed
A structured stream of product data (price, availability, attributes) a merchant exposes to be readable by engines and agents.
Machine readability
The ability of a commercial offer to be understood and used by software: structured data, explicit policies, an agent-usable endpoint.
Merchant readiness
How prepared a merchant is for agentic commerce, assessable layer by layer. See the audit methodology.
GEO (Generative Engine Optimization)
Optimization aimed at being cited and retrieved by generative engines and AI, complementing classic human-oriented SEO.
llms.txt
A text file placed at a site's root to guide language models toward reference content, modeled on robots.txt.
Merchant Center
Google's platform where a merchant declares its products; the entry point for Google's UCP reference implementation.
AI Mode
Google Search's conversational mode, one of the surfaces where UCP powers a native checkout.
Instant Checkout
The direct-purchase feature in ChatGPT launched in September 2025, powered by ACP. OpenAI scaled it back in 2026, moving it into third-party apps.
Go further
These terms make sense within a grid. Read the definition of agentic commerce or the four-layer framework.