Reference
Agentic commerce glossary: the terms in plain English
Plain-English definitions of UCP, ACP, AP2, MCP, Web Bot Auth, signed agents, merchant of record and more, with links to the guides that go deeper.
The tragent teamPublished 9 min read
When a new part of commerce forms quickly, its words arrive faster than their definitions. In 2026 a merchant reading about AI shopping agents meets a dozen acronyms, several competing names for the same idea, and terms that mean one thing to a payments team and another to a security team.
This glossary defines them plainly, as of October 2026. Filter it, jump to a letter, or link straight to a term.
The terms#
43 of 43 terms
- A2Aalso Agent2Agent
- A protocol for one AI agent to discover another and hand it a task. An agent publishes an agent card describing what it can do. Started by Google in 2025 and now a Linux Foundation project. Protocols compared
- ACPalso Agentic Commerce Protocol
- The standard from OpenAI and Stripe for listing products in ChatGPT and, originally, buying them in the chat. Since March 2026 it is mainly how catalogues reach ChatGPT; purchases complete on the merchant's site. ChatGPT shopping now
- Agent card
- A JSON document at /.well-known/agent-card.json describing an A2A agent's skills and endpoint, so other agents can find and call it. Older versions used /.well-known/agent.json.
- Agent journey
- One run of an AI agent pursuing a goal on a store, such as 'buy a black running shoe in size 10', scored stage by stage. Journeys are how a testing tool checks that an agent can actually complete a task. Testing in CI
- Agent style
- How an agent behaves while shopping: a browser agent reads and clicks pages, an API-first agent looks for structured data and protocol endpoints first. Testing several styles catches failures only one would hit.
- Agentic checkout
- A purchase completed by or through an AI agent, often inside an assistant's interface. Google's agentic checkout in AI Mode and Gemini runs on UCP with the merchant as merchant of record. Google agentic checkout
- Agentic commerce
- Buying and selling where an AI agent carries out the shopping on a person's behalf: searching, comparing, adding to a basket and, increasingly, paying within limits the person set. The full guide
- Agentic storefronts
- Shopify's feature, switched on for eligible US merchants in 2026, that makes a store's catalogue available to AI platforms such as ChatGPT through Shopify Catalog. Shopify guide
- AP2also Agent Payments Protocol
- A standard for proving that a real person authorised an agent's purchase, using signed mandates. Google contributed it to the FIDO Alliance in April 2026.
- Assistant agentalso user-triggered agent
- An AI client fetching pages because a person asked it to, right now, such as ChatGPT-User or Claude-User. Unlike a crawler, it may complete a purchase.
- Bot manager
- Security software in front of a store, such as Cloudflare, Akamai, DataDome or HUMAN, that decides whether automated requests are allowed, challenged or blocked. The most common reason agents fail at checkout. Why agents get a 403
- Browser agent
- An AI agent that uses a real or headless browser to read pages, click and fill forms, the way a person would, rather than calling APIs.
- CAPTCHA
- A challenge designed to be solvable only by a person. On a purchase path it stops every agent, signed or not; keep CAPTCHAs for abuse-prone actions such as sign-up. Fix
- Crawler
- An automated client that fetches pages to index them or collect training data, such as OAI-SearchBot, Googlebot or GPTBot. Crawlers never buy.
- Delegated payment
- A payment an agent makes with authority the shopper granted in advance, usually through a scoped token or a mandate, so the agent never holds the card itself.
- Google-Extended
- A robots.txt token, not a crawler, that controls whether Google may use your content for Gemini training and grounding. It does not affect Google Search or AI Overviews. robots.txt for agents
- GTINalso Global Trade Item Number
- A product's barcode number. In structured data and feeds it lets an agent recognise the same product across stores and compare like with like.
- Intermediary agent
- An agentic service many end users can operate, as opposed to a bot run directly by one company. Cloudflare's 2026 classification records whether access is direct or intermediary.
- JSON-LD
- The format most stores use to embed Schema.org structured data in a page, as a single script block that agents and search engines read. Product data guide
- Key directory
- A JSON Web Key Set an agent operator publishes at /.well-known/http-message-signatures-directory, holding the public keys that verify its Web Bot Auth signatures. Web Bot Auth explained
- llms.txt
- An optional Markdown file at a site's root summarising it for language models. 2026 studies found AI crawlers rarely request it and no clear link to citations. Does it work?
- Mandate
- In AP2, a signed record of what a shopper asked for, the basket offered, or the payment approved, which a merchant or bank can verify rather than taking the agent's word.
- MCPalso Model Context Protocol
- An open protocol, started by Anthropic, for AI assistants to call tools exposed by a server, such as 'search products' or 'check order status', instead of reading web pages.
- Merchant Center
- Google's tool for submitting product data. Eligibility for Google's agentic checkout is set there, product by product.
- Merchant of record
- The business legally selling the goods, taking payment and handling refunds. Under UCP and ACP the merchant stays the merchant of record; the AI platform does not resell your products.
- native_commerce(checkout_eligibility)
- The Merchant Center product attribute that opts a product into Google's agentic checkout. Missing or FALSE means not eligible.
- Product feed
- A file of your products, prices and stock sent to a platform such as Google Merchant Center or OpenAI. Agents compare it with your pages, so the two should agree.
- Protocol agent
- An agent that shops through a commerce protocol such as UCP or MCP rather than by rendering your website.
- Readiness score
- A single number summarising how well a store works for AI agents. Scores from different tools measure different things and are not comparable. Tools compared
- Regression gate
- A CI rule that fails a build when a stage gets worse compared with an accepted baseline, rather than whenever a score is below a threshold.
- Revenue at risk
- An estimate of the monthly sales lost when agents fail on a store, computed so each lost order is counted once, at the first stage that blocks it. Calculator
- robots.txt
- A file telling crawlers which paths not to fetch. It is a request, not enforcement: a bot manager applies its own rules regardless.
- Schema.org
- The shared vocabulary for structured data. Product, Offer and ItemAvailability are the types agents rely on most to read a product's identity, price and stock.
- Signature-Agent
- The HTTP header in which a signed request names its operator's origin, for example sig1="https://chatgpt.com". Verifiers fetch the key directory from it.
- Signed agent
- An agent whose requests carry a cryptographic Web Bot Auth signature that can be verified against its operator's published keys. Proof of identity, not of intent.
- Stage
- One of the nine steps an agent purchase passes through: find products, read the details, see the price, check stock, add to basket, reach checkout, pay, return an order, and sign in.
- Structured data
- Machine-readable facts embedded in a page, usually Schema.org in JSON-LD, so software can read a product's name, price and availability without guessing from text.
- UCPalso Universal Commerce Protocol
- The open standard from Google, Shopify and partners for an agent to discover a store, browse, build a basket and check out, with the merchant as seller. It powers Google's agentic checkout. Protocols compared
- User agent
- The free-text header in which a client names itself, such as ChatGPT-User/1.0. Anyone can send any value, so it is a claim, not proof.
- Verified bot
- A bot a bot manager has confirmed is who it says it is. Since July 2026 Cloudflare counts signed agents as verified, with a field recording direct or intermediary access.
- Web Bot Auth
- The profile of HTTP Message Signatures (RFC 9421) that bots and agents use to sign requests, being standardised in the IETF's Web Bot Auth working group. Explained
- WebMCPalso Web Model Context Protocol
- A draft web standard for pages to declare actions a browser agent can call. Shopify shipped WebMCP checkout tools in September 2026.
Which terms are most often confused?#
Five pairs cause most of the misunderstandings. Getting these straight makes the rest of the vocabulary easier.
- Crawler vs assistant agent. A crawler indexes or collects content and never buys. An assistant agent fetches a page because a person asked, and may complete a purchase. They need different robots rules and should be measured separately.
- Verified bot vs signed agent. A signed agent proves its identity cryptographically on each request. A verified bot is one a bot manager has confirmed, by signature or other means. Since mid-2026 Cloudflare treats signed agents as a kind of verified bot.
- User agent vs Signature-Agent. The user agent is a claim anyone can make. The
Signature-Agentheader, with a signature that verifies, is proof. - UCP vs ACP. Both describe agents shopping, but on different surfaces: UCP powers Google's agentic checkout, ACP feeds catalogues into ChatGPT.
- Merchant of record vs platform. The merchant of record sells the goods and owns the customer relationship. Under today's protocols that stays the merchant, not the AI platform.
Which terms matter most for a store owner?#
Bot manager, structured data and stage. Most of the work of selling to agents comes down to three things: letting agents through your bot manager, publishing complete structured data, and making sure every stage of the purchase works for an agent. The protocols matter on specific surfaces, and most platforms implement them for you.
If you read one guide after this glossary, make it why AI shopping agents get a 403 at your checkout. It covers the failure most stores have.
Which terms matter most for an engineer?#
Web Bot Auth, conformance and regression gate. Engineers own the parts that break silently: verifying signed agents at the edge, keeping protocol integrations conformant as specs version, and adding a regression gate so a deploy that breaks agents fails like any other broken build.
The guide to testing your store with AI shopping agents in CI shows how to wire that into GitHub Actions.
How do we keep this glossary current?#
We re-check it whenever a protocol or platform changes, and the date at the top says when. Agentic commerce moved fast in 2026: checkout in ChatGPT was scaled back, Google launched agentic checkout, AP2 moved to the FIDO Alliance, and Web Bot Auth became an IETF working-group draft. Where a definition depends on a fast-moving fact, we date it in the text. If a term is missing or wrong, our editorial policy says how to tell us.
Frequently asked questions
- What does agentic commerce mean?
- Buying and selling where an AI agent does the shopping on a person's behalf: searching, comparing, adding to a basket and increasingly paying, within limits the person set.
- What is the difference between UCP and ACP?
- UCP is the open standard from Google and Shopify that powers agentic checkout in Google AI Mode and Gemini. ACP is the OpenAI and Stripe standard used mainly to list products in ChatGPT.
- What is a signed agent?
- An AI agent whose requests carry a Web Bot Auth signature that a website can verify against the operator's published keys, proving which operator sent the request.
- What is a merchant of record?
- The business that legally sells the goods, takes the payment and handles refunds. Under UCP and ACP the merchant remains the merchant of record when an AI agent buys.
- What is the difference between a crawler and an AI agent?
- A crawler fetches pages to index them or collect training data and never buys. An assistant agent acts for a person in the moment and may complete a purchase.
Sources
- Universal Commerce Protocol — UCP Authors
- Agentic Commerce Protocol — OpenAI and Stripe
- FIDO Alliance to develop standards for trusted AI agent interactions — FIDO Alliance
- HTTP Message Signatures for Bots — IETF Web Bot Auth working group
- Verified bots — Cloudflare docs
- Prepare your Merchant Center account for UCP — Google for Developers
Written by the tragent team and checked against the sources listed above on October 19, 2026. See how we write and correct posts in our editorial policy.