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. 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. Powers Instant Checkout in ChatGPT.
AP2 (Agent Payments Protocol)
Open protocol from Google and 60+ partners (September 2025) to authorize agent-initiated payments via cryptographic mandates. The payment layer.
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.
x402
An AP2-linked extension, backed by Coinbase, for machine-to-machine stablecoin settlement. The settlement layer.
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, powered by OpenAI and Stripe's ACP protocol.
Go further
These terms make sense within a grid. Read the definition of agentic commerce or the four-layer framework.