# Agentic commerce glossary, A to Z

About fifty terms from agentic commerce, from A2A to x402, each defined in its source’s words with its status label, an anchor you can link to, and the article that covers it.

By Valerii Checha, 3 Nov 2026

Agentic commerce comes with a lot of acronyms, and new ones turn up faster than anyone can learn them. Here are 52 terms, from A2A to x402, each with a short definition, a quote from its own source where there is one, and a link to the article or check that covers it.

Every term has its own anchor, so `/blog/agentic-commerce-glossary#ucp` opens at UCP. Status labels such as beta or preview are the sources' own. Where we explain a term in plain words, the explanation is ours. If you are new to the series, start with [what is agentic commerce?](https://storewalk.ai/blog/what-is-agentic-commerce) or [the hub article](https://storewalk.ai/blog/why-agents-cant-buy).

Find a term.

The basics:

- [Agent readiness](https://storewalk.ai/blog/agentic-commerce-glossary#agent-readiness)
- [Agentic commerce](https://storewalk.ai/blog/agentic-commerce-glossary#agentic-commerce)
- [Crawler and agent](https://storewalk.ai/blog/agentic-commerce-glossary#crawler-vs-agent)
- [Merchant Center](https://storewalk.ai/blog/agentic-commerce-glossary#merchant-center)
- [Merchant of record](https://storewalk.ai/blog/agentic-commerce-glossary#merchant-of-record)
- [Product feed](https://storewalk.ai/blog/agentic-commerce-glossary#product-feed)
- [Shopping Graph](https://storewalk.ai/blog/agentic-commerce-glossary#shopping-graph)

Reading a page:

- [JSON-LD](https://storewalk.ai/blog/agentic-commerce-glossary#json-ld)
- [llms.txt](https://storewalk.ai/blog/agentic-commerce-glossary#llms-txt)
- [Markdown negotiation](https://storewalk.ai/blog/agentic-commerce-glossary#markdown-negotiation)
- [Product schema](https://storewalk.ai/blog/agentic-commerce-glossary#product-schema)
- [Structured data](https://storewalk.ai/blog/agentic-commerce-glossary#structured-data)

Bots and identity:

- [AIPREF](https://storewalk.ai/blog/agentic-commerce-glossary#aipref)
- [Bot management](https://storewalk.ai/blog/agentic-commerce-glossary#bot-management)
- [CAPTCHA](https://storewalk.ai/blog/agentic-commerce-glossary#captcha)
- [Content Signals](https://storewalk.ai/blog/agentic-commerce-glossary#content-signals)
- [HTTP Message Signatures (RFC 9421)](https://storewalk.ai/blog/agentic-commerce-glossary#http-message-signatures)
- [OAuth 2.0](https://storewalk.ai/blog/agentic-commerce-glossary#oauth)
- [Protected resource metadata (RFC 9728)](https://storewalk.ai/blog/agentic-commerce-glossary#protected-resource-metadata)
- [robots.txt](https://storewalk.ai/blog/agentic-commerce-glossary#robots-txt)
- [Signed agents and verified bots](https://storewalk.ai/blog/agentic-commerce-glossary#verified-bots)
- [User agent](https://storewalk.ai/blog/agentic-commerce-glossary#user-agent)
- [Web Bot Auth](https://storewalk.ai/blog/agentic-commerce-glossary#web-bot-auth)

Discovery and tools:

- [A2A (Agent2Agent)](https://storewalk.ai/blog/agentic-commerce-glossary#a2a)
- [Agent card](https://storewalk.ai/blog/agentic-commerce-glossary#agent-card)
- [API catalog](https://storewalk.ai/blog/agentic-commerce-glossary#api-catalog)
- [Link header](https://storewalk.ai/blog/agentic-commerce-glossary#link-header)
- [MCP (Model Context Protocol)](https://storewalk.ai/blog/agentic-commerce-glossary#mcp)
- [MCP server card](https://storewalk.ai/blog/agentic-commerce-glossary#mcp-server-card)
- [WebMCP](https://storewalk.ai/blog/agentic-commerce-glossary#webmcp)
- [Well-known URI (RFC 8615)](https://storewalk.ai/blog/agentic-commerce-glossary#well-known-uri)

Checkout:

- [ACP (Agentic Commerce Protocol)](https://storewalk.ai/blog/agentic-commerce-glossary#acp)
- [Agentic checkout](https://storewalk.ai/blog/agentic-commerce-glossary#agentic-checkout)
- [Buy for Me (Amazon)](https://storewalk.ai/blog/agentic-commerce-glossary#buy-for-me)
- [continue_url](https://storewalk.ai/blog/agentic-commerce-glossary#continue-url)
- [Copilot Checkout](https://storewalk.ai/blog/agentic-commerce-glossary#copilot-checkout)
- [Guest checkout](https://storewalk.ai/blog/agentic-commerce-glossary#guest-checkout)
- [Instant Buy (Perplexity)](https://storewalk.ai/blog/agentic-commerce-glossary#instant-buy)
- [Instant Checkout (ChatGPT)](https://storewalk.ai/blog/agentic-commerce-glossary#instant-checkout)
- [UCP (Universal Commerce Protocol)](https://storewalk.ai/blog/agentic-commerce-glossary#ucp)
- [Universal Cart (Google)](https://storewalk.ai/blog/agentic-commerce-glossary#universal-cart)

Payment:

- [Agent Pay (Mastercard)](https://storewalk.ai/blog/agentic-commerce-glossary#agent-pay)
- [AP2 (Agent Payments Protocol)](https://storewalk.ai/blog/agentic-commerce-glossary#ap2)
- [Delegated payment](https://storewalk.ai/blog/agentic-commerce-glossary#delegated-payment)
- [Mandate (AP2)](https://storewalk.ai/blog/agentic-commerce-glossary#mandate)
- [MPP (Machine Payments Protocol)](https://storewalk.ai/blog/agentic-commerce-glossary#mpp)
- [Network token](https://storewalk.ai/blog/agentic-commerce-glossary#network-token)
- [PSP (payment service provider)](https://storewalk.ai/blog/agentic-commerce-glossary#psp)
- [Shared Payment Token (SPT)](https://storewalk.ai/blog/agentic-commerce-glossary#spt)
- [Trusted Agent Protocol (Visa)](https://storewalk.ai/blog/agentic-commerce-glossary#trusted-agent-protocol)
- [Visa Intelligent Commerce](https://storewalk.ai/blog/agentic-commerce-glossary#visa-intelligent-commerce)
- [x402](https://storewalk.ai/blog/agentic-commerce-glossary#x402)

## The terms, A to Z

### A2A (Agent2Agent)

An open protocol for agents to talk to each other. Its specification calls it "an open standard designed to facilitate communication and interoperability between independent, potentially opaque AI agent systems", and labels 1.0.0 its "Latest Released Version". See [MCP, A2A and WebMCP for stores](https://storewalk.ai/blog/mcp-a2a-webmcp-for-stores).

### ACP (Agentic Commerce Protocol)

A checkout protocol whose README describes it as "an interaction model and open standard for connecting buyers, their AI agents, and businesses to complete purchases seamlessly". Its maintainers file lists OpenAI, Stripe and Meta, and the README says it "is currently in beta". See [ACP explained](https://storewalk.ai/blog/acp-explained).

### Agent card

A2A's description of an agent, which the specification calls "A self-describing manifest for an agent". It can be published at `/.well-known/agent-card.json`. See [MCP, A2A and WebMCP for stores](https://storewalk.ai/blog/mcp-a2a-webmcp-for-stores) and our [A2A agent card check](https://storewalk.ai/checks/DISC-013).

### Agent Pay (Mastercard)

Mastercard's programme for agent payments. Its April 2025 announcement calls it "its Agentic Payments Program, Mastercard Agent Pay", and says it "introduces Mastercard Agentic Tokens". See [how an agent pays without seeing your card](https://storewalk.ai/blog/how-agents-pay).

### Agent readiness

How well an AI agent can use a site for a person; that wording is ours, because the term has no standard meaning. Cloudflare says its score shows "how well their websites support AI agents", and specification.website calls it "the set of choices that make a site legible to AI agents and LLMs". See [what is agent readiness, and how is it measured?](https://storewalk.ai/blog/what-is-agent-readiness), or run our [agent readiness scanner](https://storewalk.ai/) on your own store.

### Agentic checkout

A name two companies use for different things. In OpenAI's docs, the Agentic Checkout Spec "enables ChatGPT to act as the customer's AI agent and renders a checkout experience embedded in ChatGPT's UI"; Google uses "agentic checkout" for a price-tracked item, where it offers "the option to have Google buy it for you on the merchant's site using Google Pay". See [why agents stall at checkout](https://storewalk.ai/blog/why-agents-stall-at-checkout).

### Agentic commerce

Shopping done by an AI agent on a person's behalf (our wording). Google describes it as "where AI completes tasks on people's behalf"; Stripe, Shopify, Visa and Forrester each word it differently, and none of them says who coined it. See [what is agentic commerce?](https://storewalk.ai/blog/what-is-agentic-commerce)

### AIPREF

An IETF working group drafting a vocabulary for AI usage preferences and ways to attach them to content, in robots.txt or HTTP headers. Its vocabulary draft is `draft-ietf-aipref-vocab-08`, and it says "Preferences are not a security mechanism." See [how agents discover what a store offers](https://storewalk.ai/blog/how-agents-discover-a-store).

### AP2 (Agent Payments Protocol)

A payment protocol its site calls "an open protocol for the emerging Agent Economy". Version 0.2 defines two signed authorisations, the Checkout Mandate and the Payment Mandate. Google donated it to the FIDO Alliance in April 2026. See [how an agent pays](https://storewalk.ai/blog/how-agents-pay).

### API catalog

A list of a publisher's APIs at `/.well-known/api-catalog`, defined in RFC 9727 "to facilitate automated discovery and usage of published Application Programming Interfaces (APIs)". See [how agents discover what a store offers](https://storewalk.ai/blog/how-agents-discover-a-store) and our [API catalog check](https://storewalk.ai/checks/DISC-011).

### Bot management

Tools that tell automated traffic from people and decide what to do with it. Cloudflare's docs define bots as "automated software that sends requests to your site" and say its bot solutions "detect this automated traffic and let you decide how to respond." See [why agents stall at checkout](https://storewalk.ai/blog/why-agents-stall-at-checkout).

### Buy for Me (Amazon)

An Amazon feature that buys from other brands' websites inside the Amazon Shopping app. Amazon calls it a "New beta feature" for "a subset of U.S. customers", and says it provides "the customer's encrypted name, address, and payment details to complete the checkout process on the brand's website." See [what is agentic commerce?](https://storewalk.ai/blog/what-is-agentic-commerce)

### CAPTCHA

A challenge meant to tell a person from a program; the name stands for "Completely Automated Public Turing Test, to Tell Computers and Humans Apart", as the W3C's Group Draft Note of 16 December 2021 spells it out. Our [CAPTCHA check](https://storewalk.ai/checks/TRX-002) looks for one before the payment step.

### Content Signals

Cloudflare's lines for robots.txt, "a set of machine-readable directives in a robots.txt file that categorize how crawlers may use your content", in three categories: search, ai-input and ai-train. Its site says some systems "may ignore these Content-Signal directives." See [how agents discover what a store offers](https://storewalk.ai/blog/how-agents-discover-a-store).

### continue_url

The address in a UCP checkout where the buyer takes over from the agent. The specification says it "enables checkout handoff from platform to business UI, allowing the buyer to continue and finalize the checkout session", and that it "MUST be an absolute HTTPS URL". See [UCP explained](https://storewalk.ai/blog/ucp-explained).

### Copilot Checkout

Microsoft's checkout inside Copilot. On 8 January 2026 Microsoft wrote that it "is beginning to roll out in the U.S. on Copilot.com". See [what is agentic commerce?](https://storewalk.ai/blog/what-is-agentic-commerce)

### Crawler and agent

Two kinds of automated visitor (the split is ours). A training crawler collects pages in bulk: OpenAI's GPTBot "is used to crawl content that may be used in training our generative AI foundation models". An agent fetches because a person asked: Cloudflare calls agents "software acting on behalf of people". See [bots, crawlers and agents](https://storewalk.ai/blog/bots-crawlers-agents).

### Delegated payment

Handing an agent a limited right to pay instead of the card itself. OpenAI's Delegated Payment Spec "allows OpenAI to securely share payment details with the merchant or its designated payment service provider (PSP)"; in ACP, the delegate payment call returns a token limited by an allowance. See [ACP explained](https://storewalk.ai/blog/acp-explained).

### Guest checkout

Buying without an account. BigCommerce's setting reads "Customers are not required to have an account to check out". An agent shopping for someone may have no account on your store, so a required sign-in can stop it. See our [guest checkout check](https://storewalk.ai/checks/TRX-001).

### HTTP Message Signatures (RFC 9421)

A Standards Track RFC from February 2024 that defines "a mechanism for creating, encoding, and verifying digital signatures or message authentication codes over components of an HTTP message". Web Bot Auth builds on it. See [bots, crawlers and agents](https://storewalk.ai/blog/bots-crawlers-agents).

### Instant Buy (Perplexity)

Perplexity's in-app purchase: it "lets U.S. users search for and buy products from a wide range of merchants directly on Perplexity", and "is currently available to all users in the United States." See [what is agentic commerce?](https://storewalk.ai/blog/what-is-agentic-commerce)

### Instant Checkout (ChatGPT)

OpenAI's name for buying inside ChatGPT. Its developer docs say "Supporting Instant Checkout in ChatGPT requires a merchant to implement three flows." Whether it is still offered is not published on the pages we could read. See [ACP explained](https://storewalk.ai/blog/acp-explained).

### JSON-LD

The format Google recommends for structured data, which it describes as "A JavaScript notation embedded in a `<script>` tag" in the page. See [how an AI agent reads a web page](https://storewalk.ai/blog/how-agents-read-a-page).

### Link header

An HTTP response header, defined in RFC 8288, that points from one resource to another with a relation type, such as `rel="api-catalog"`. A store can use it to point agents at its discovery files. See our [Link headers check](https://storewalk.ai/checks/DISC-010).

### llms.txt

A proposed file at `/llms.txt` with background on a site and links to Markdown versions of its pages. It is a proposal by Jeremy Howard, "The /llms.txt file, v2", modified 10 August 2026, not a standards-body document. See our [llms.txt check](https://storewalk.ai/checks/DISC-002).

### Mandate (AP2)

AP2's signed authorisation for a purchase. Version 0.2 says "AP2 defines two Mandate types: Checkout Mandate and Payment Mandate": the first goes to the merchant, the second to the credential provider and the card networks. See [how an agent pays](https://storewalk.ai/blog/how-agents-pay).

### Markdown negotiation

Asking a server for a page as Markdown by sending `Accept: text/markdown`. Cloudflare's Markdown for Agents does this for enabled zones: it fetches the HTML "and convert it to Markdown before serving it to the client". See our [Markdown check](https://storewalk.ai/checks/DISC-009).

### MCP (Model Context Protocol)

"an open protocol that enables seamless integration between LLM applications and external data sources and tools". Its current revision is 2026-07-28, and it is stewarded by the Agentic AI Foundation under the Linux Foundation. See [MCP, A2A and WebMCP for stores](https://storewalk.ai/blog/mcp-a2a-webmcp-for-stores).

### MCP server card

A static document that describes a remote MCP server before anyone connects to it, defined in SEP-2127, which "has reached Final status" as an optional extension. A domain can list its cards in an AI Catalog at `/.well-known/ai-catalog.json`. See our [MCP server card check](https://storewalk.ai/checks/DISC-012).

### Merchant Center

Google's product data service: "a free tool that helps millions of shoppers on Google discover, explore, and buy your products." Google's UCP checkout shows a Buy button only for listings with the `native_commerce(checkout_eligibility)` product attribute. See [what is agentic commerce?](https://storewalk.ai/blog/what-is-agentic-commerce)

### Merchant of record

The party that sells to the buyer and is responsible for the sale (our wording). UCP says "The business remains the Merchant of Record (MoR)", and ACP's site says businesses "maintain their customer relationships as the merchant of record". See [UCP vs ACP vs MCP vs AP2](https://storewalk.ai/blog/ucp-vs-acp-vs-mcp-vs-ap2).

### MPP (Machine Payments Protocol)

Stripe describes it as "an open protocol that lets agents pay for your APIs and services programmatically without a checkout UI, co-authored by Stripe and Tempo". It uses HTTP status 402. See our [MPP check](https://storewalk.ai/checks/TRX-006).

### Network token

A stand-in for a card number issued through the card networks. Adyen's docs say "A network token is 16-digit alternative for the Primary Account Number (PAN), and is unique per combination of shopper and merchant." See [how an agent pays](https://storewalk.ai/blog/how-agents-pay).

### OAuth 2.0

The authorisation framework of RFC 6749 (Standards Track, October 2012), which "enables a third-party application to obtain limited access to an HTTP service". MCP's authorisation builds on it. See our [OAuth metadata check](https://storewalk.ai/checks/TRX-007).

### Product feed

A structured file of your products sent to a platform (our wording). OpenAI's docs say product feeds "give ChatGPT the catalog data it needs to index your products", and that onboarding "is currently available to approved partners." See [what is agentic commerce?](https://storewalk.ai/blog/what-is-agentic-commerce)

### Product schema

The schema.org type for a product, defined as "Any offered product or service", with an Offer for price, currency and availability. It is what product structured data usually describes. See our [product structured data check](https://storewalk.ai/checks/DISC-004).

### Protected resource metadata (RFC 9728)

A Standards Track RFC from April 2025: "a metadata format that an OAuth 2.0 client or authorization server can use to obtain the information needed to interact with an OAuth 2.0 protected resource", by default at `/.well-known/oauth-protected-resource`. MCP authorisation requires it. See our [protected resource check](https://storewalk.ai/checks/TRX-008).

### PSP (payment service provider)

The company that processes a store's card payments. ACP's terminology defines it as a "Service processing payment transactions (e.g., Stripe, Adyen)". See our [payment provider check](https://storewalk.ai/checks/TRX-003).

### robots.txt

A file of crawl rules at the root of a site, standardised in RFC 9309 as rules "that crawlers are requested to honor". The RFC adds: "These rules are not a form of access authorization." See [bots, crawlers and agents](https://storewalk.ai/blog/bots-crawlers-agents) and our [robots.txt check](https://storewalk.ai/checks/DISC-001).

### Shared Payment Token (SPT)

Stripe's token for agent purchases: "SPTs grant sellers scoped access to customers' payment methods for agent-initiated purchases". Stripe labels it a preview. See [how an agent pays](https://storewalk.ai/blog/how-agents-pay).

### Shopping Graph

Google's product dataset. On 15 October 2026 Google said it holds "60+ billion continually refreshed product listings". See [what is agentic commerce?](https://storewalk.ai/blog/what-is-agentic-commerce)

### Signed agents and verified bots

Cloudflare's names for automated visitors it can identify. A verified bot "declares who it is deterministically, through a cryptographic Web Bot Auth signature, a published IP list with a stable user-agent, or reverse DNS", and Cloudflare says "Signed agents are now Verified As of July 1, 2026". See [bots, crawlers and agents](https://storewalk.ai/blog/bots-crawlers-agents).

### Structured data

Google: "Structured data is a standardized format for providing information about a page and classifying the page content". For a store, it is how a page states price and stock for a program to read. See [how an AI agent reads a web page](https://storewalk.ai/blog/how-agents-read-a-page).

### Trusted Agent Protocol (Visa)

Visa's "verifiable, cryptographic standard to help merchants differentiate legitimate agents from nefarious bots or web crawlers", which builds on RFC 9421. See [how an agent pays](https://storewalk.ai/blog/how-agents-pay).

### UCP (Universal Commerce Protocol)

A commerce protocol Google calls "a new open standard for agentic commerce that works across the entire shopping journey", developed with Shopify. A store publishes its profile at `/.well-known/ucp`; the current release on GitHub is v2026-08-25. See [UCP explained](https://storewalk.ai/blog/ucp-explained) and our [discovery check](https://storewalk.ai/checks/DISC-007).

### Universal Cart (Google)

Google's shopping cart. On 15 October 2026 Google said it "is rolling out in the U.S. across Google Search and in the Gemini app", with checkout "powered by the Universal Commerce Protocol (UCP)". See [what is agentic commerce?](https://storewalk.ai/blog/what-is-agentic-commerce)

### User agent

The name a program sends with each request. RFC 9110 says the header "contains information about the user agent originating the request"; the program declares it itself, so it can be copied. See [bots, crawlers and agents](https://storewalk.ai/blog/bots-crawlers-agents).

### Visa Intelligent Commerce

Visa's agent programmes, which Visa calls "our strategic portfolio for the age of AI agents". See [how an agent pays](https://storewalk.ai/blog/how-agents-pay).

### Web Bot Auth

An IETF draft "to allow automated HTTP clients to cryptographically sign outbound requests, allowing HTTP servers to verify their identity with confidence." It is `draft-ietf-webbotauth-httpsig-protocol-00`, a working-group document. See [bots, crawlers and agents](https://storewalk.ai/blog/bots-crawlers-agents) and our [key directory check](https://storewalk.ai/checks/VER-002).

### WebMCP

A browser API that lets a page offer tools to agents: pages using it "can be thought of as Model Context Protocol \[MCP] servers that implement tools in client-side script". It is a Draft Community Group Report, "not a W3C Standard". See our [WebMCP check](https://storewalk.ai/checks/DISC-015).

### Well-known URI (RFC 8615)

The `/.well-known/` path prefix for site-wide metadata, defined in RFC 8615. New names "MUST register" with IANA. UCP, A2A and API catalogs use it. See [how agents discover what a store offers](https://storewalk.ai/blog/how-agents-discover-a-store).

### x402

A payment scheme over HTTP status 402 that its site calls an "open, neutral standard for internet-native payments", now run by the x402 Foundation. It is aimed at paying for APIs and content. See our [x402 check](https://storewalk.ai/checks/TRX-005).

## Which of these are standards, and which are drafts?

The terms above sit at very different stages. Some are finished RFCs, some are drafts, and some are a company's product with its own label. Pick a kind of label to see which specifications carry it, in their own words. The grouping is ours.

Status at a glance: each specification by its own label.

Published standards. In our words: Finished documents from a standards body. They can still be updated by a later one.

- [Well-known URIs, RFC 8615](https://storewalk.ai/blog/agentic-commerce-glossary#well-known-uri): Standards Track, May 2019. Source: [RFC 8615](https://www.rfc-editor.org/rfc/rfc8615).
- [OAuth 2.0, RFC 6749](https://storewalk.ai/blog/agentic-commerce-glossary#oauth): Standards Track, October 2012. Source: [RFC 6749](https://www.rfc-editor.org/rfc/rfc6749).
- [robots.txt, RFC 9309](https://storewalk.ai/blog/agentic-commerce-glossary#robots-txt): Standards Track, September 2022. Source: [RFC 9309](https://www.rfc-editor.org/rfc/rfc9309).
- [HTTP Message Signatures, RFC 9421](https://storewalk.ai/blog/agentic-commerce-glossary#http-message-signatures): Standards Track, February 2024. Source: [RFC 9421](https://www.rfc-editor.org/rfc/rfc9421).
- [Protected resource metadata, RFC 9728](https://storewalk.ai/blog/agentic-commerce-glossary#protected-resource-metadata): Standards Track, April 2025. Source: [RFC 9728](https://www.rfc-editor.org/rfc/rfc9728).
- [API catalog, RFC 9727](https://storewalk.ai/blog/agentic-commerce-glossary#api-catalog): Standards Track, June 2025. Source: [RFC 9727](https://www.rfc-editor.org/rfc/rfc9727).

Drafts and notes. In our words: Work in progress at a standards body, or a group report that is not on a standards track.

- [Web Bot Auth](https://storewalk.ai/blog/agentic-commerce-glossary#web-bot-auth): draft-ietf-webbotauth-httpsig-protocol-00, a working-group document. Source: [IETF datatracker: Web Bot Auth draft](https://datatracker.ietf.org/doc/draft-ietf-webbotauth-httpsig-protocol/).
- [AIPREF vocabulary](https://storewalk.ai/blog/agentic-commerce-glossary#aipref): draft-ietf-aipref-vocab-08, a working-group document. Source: [draft-ietf-aipref-vocab-08](https://www.ietf.org/archive/id/draft-ietf-aipref-vocab-08.txt).
- [WebMCP](https://storewalk.ai/blog/agentic-commerce-glossary#webmcp): Draft Community Group Report; “not a W3C Standard nor is it on the W3C Standards Track”. Source: [WebMCP draft](https://webmachinelearning.github.io/webmcp/).
- [CAPTCHA note](https://storewalk.ai/blog/agentic-commerce-glossary#captcha): W3C Group Draft Note, 16 December 2021. Source: [W3C: Inaccessibility of CAPTCHA](https://www.w3.org/TR/turingtest/).

Versioned specifications. In our words: Published by their own project, versioned by date or number, with the project’s own label.

- [MCP](https://storewalk.ai/blog/agentic-commerce-glossary#mcp): Current revision 2026-07-28; server cards (SEP-2127) at Final. Source: [MCP specification: versioning](https://modelcontextprotocol.io/specification/versioning).
- [A2A](https://storewalk.ai/blog/agentic-commerce-glossary#a2a): Latest Released Version 1.0.0. Source: [A2A specification](https://a2a-protocol.org/latest/specification/).
- [UCP](https://storewalk.ai/blog/agentic-commerce-glossary#ucp): Release v2026-08-25, marked “Latest” on GitHub. Source: [UCP releases on GitHub](https://github.com/Universal-Commerce-Protocol/ucp/releases).
- [AP2](https://storewalk.ai/blog/agentic-commerce-glossary#ap2): v0.2, with no draft or final label. Source: [AP2 specification](https://ap2-protocol.org/ap2/specification/).

Vendor labels. In our words: A company’s own product label, such as beta or preview, or a proposal by one author.

- [ACP](https://storewalk.ai/blog/agentic-commerce-glossary#acp): “currently in beta”; latest stable version 2026-04-17. Source: [ACP repository and README](https://github.com/agentic-commerce-protocol/agentic-commerce-protocol).
- [Stripe Shared Payment Tokens](https://storewalk.ai/blog/agentic-commerce-glossary#spt): preview. Source: [Stripe docs: Shared payment tokens](https://docs.stripe.com/agentic-commerce/concepts/shared-payment-tokens).
- [llms.txt](https://storewalk.ai/blog/agentic-commerce-glossary#llms-txt): A proposal by Jeremy Howard, v2, modified 10 August 2026. Source: [The /llms.txt file, v2](https://llmstxt.org/).

A vendor's "beta" can outlast the time some standards take to write, so read the label as a guide to how much a term may still change.

## Which terms do people mix up?

Some pairs sound alike and do different jobs. Each side below is in its source's words; the line under each pair is ours.

Terms people mix up, side by side.

- Crawler or agent? Training crawler: OpenAI: GPTBot “is used to crawl content that may be used in training our generative AI foundation models”. Agent: Cloudflare: agents are “software acting on behalf of people”. In our words: a crawler collects pages in bulk; an agent fetches a page because a person asked for something.
- ACP or AP2? ACP: “an interaction model and open standard for connecting buyers, their AI agents, and businesses to complete purchases seamlessly”. AP2: “an open protocol for the emerging Agent Economy”, with two mandates: a Checkout Mandate and a Payment Mandate. In our words: ACP runs the checkout session; AP2 is about proving the shopper authorised the purchase.
- Shared Payment Token or network token? Shared Payment Token: Stripe: “SPTs grant sellers scoped access to customers’ payment methods for agent-initiated purchases” (preview). Network token: Adyen: “A network token is 16-digit alternative for the Primary Account Number (PAN), and is unique per combination of shopper and merchant.” In our words: an SPT is a Stripe object made for one agent purchase; a network token stands in for a card number across many payments.
- Content Signals or AIPREF? Content Signals: Cloudflare: “a set of machine-readable directives in a robots.txt file that categorize how crawlers may use your content.” AIPREF: IETF working-group drafts for a vocabulary of AI usage preferences. They say: “Preferences are not a security mechanism.” In our words: one is a company’s directive format in use today; the other is a standards-body draft for the same idea.
- Instant Checkout or Instant Buy? Instant Checkout (ChatGPT): OpenAI: “Supporting Instant Checkout in ChatGPT requires a merchant to implement three flows.” Whether it is still offered is not published. Instant Buy (Perplexity): Perplexity: “Instant Buy lets U.S. users search for and buy products from a wide range of merchants directly on Perplexity”. In our words: similar names, two companies, two different programmes.

## Frequently asked questions

### What is the difference between UCP and ACP?

Both define how an agent checks out with a store, and both keep the store as merchant of record. UCP was developed by Google with Shopify and uses a profile at `/.well-known/ucp`; ACP's maintainers file lists OpenAI, Stripe and Meta, and it labels itself beta. [UCP vs ACP vs MCP vs AP2](https://storewalk.ai/blog/ucp-vs-acp-vs-mcp-vs-ap2) compares them.

### Is llms.txt a standard?

No. It is a proposal by its author, Jeremy Howard, in its second version. Google says you don't need "AI text files" to appear in its AI features.

### What is a merchant of record?

The party that sells to the buyer and is responsible for the sale; that wording is ours. UCP's checkout specification says "The business remains the Merchant of Record (MoR)", and ACP's site says businesses "maintain their customer relationships as the merchant of record". So when an agent buys through either protocol, the sale is still yours.

### What is the difference between a web crawler and an AI agent?

The split is ours, but the vendors' wordings support it. A training crawler such as OpenAI's GPTBot collects pages in bulk; GPTBot "is used to crawl content that may be used in training our generative AI foundation models". An agent fetches because a person asked, and Cloudflare calls agents "software acting on behalf of people". [Bots, crawlers and agents](https://storewalk.ai/blog/bots-crawlers-agents) covers which is which in your robots.txt.

The sources below were last checked on the date shown.

## Sources

- [A2A specification](https://a2a-protocol.org/latest/specification/)
- [ACP repository and README](https://github.com/agentic-commerce-protocol/agentic-commerce-protocol)
- [Agentic Checkout API, 2026-04-17](https://github.com/agentic-commerce-protocol/agentic-commerce-protocol/blob/main/spec/2026-04-17/openapi/openapi.agentic_checkout.yaml)
- [agenticcommerce.dev](https://www.agenticcommerce.dev/)
- [AP2 specification (v0.2)](https://ap2-protocol.org/ap2/specification/)
- [UCP specification overview](https://ucp.dev/latest/specification/overview/)
- [UCP checkout capability](https://ucp.dev/latest/specification/shopping/checkout/)
- [MCP specification](https://modelcontextprotocol.io/specification/latest)
- [MCP SEP-2127: Server Cards](https://modelcontextprotocol.io/seps/2127-mcp-server-cards)
- [WebMCP, Draft Community Group Report](https://webmachinelearning.github.io/webmcp/)
- [RFC 6749: OAuth 2.0](https://www.rfc-editor.org/rfc/rfc6749)
- [RFC 8288: Web Linking](https://www.rfc-editor.org/rfc/rfc8288)
- [RFC 8615: Well-Known URIs](https://www.rfc-editor.org/rfc/rfc8615)
- [RFC 9110: HTTP Semantics](https://www.rfc-editor.org/rfc/rfc9110)
- [RFC 9309: Robots Exclusion Protocol](https://www.rfc-editor.org/rfc/rfc9309)
- [RFC 9421: HTTP Message Signatures](https://www.rfc-editor.org/rfc/rfc9421)
- [RFC 9727: api-catalog](https://www.rfc-editor.org/rfc/rfc9727)
- [RFC 9728: OAuth 2.0 Protected Resource Metadata](https://www.rfc-editor.org/rfc/rfc9728)
- [IETF datatracker: draft-ietf-webbotauth-httpsig-protocol](https://datatracker.ietf.org/doc/draft-ietf-webbotauth-httpsig-protocol/)
- [draft-ietf-aipref-vocab-08](https://www.ietf.org/archive/id/draft-ietf-aipref-vocab-08.txt)
- [W3C Group Draft Note: Inaccessibility of CAPTCHA](https://www.w3.org/TR/turingtest/)
- [The /llms.txt file, v2](https://llmstxt.org/)
- [Cloudflare docs: Markdown for Agents](https://developers.cloudflare.com/fundamentals/reference/markdown-for-agents/)
- [Cloudflare docs: Bots](https://developers.cloudflare.com/bots/)
- [Cloudflare docs: Verified bots](https://developers.cloudflare.com/bots/concepts/bot/verified-bots/)
- [contentsignals.org](https://contentsignals.org/)
- [OpenAI: Overview of OpenAI crawlers](https://developers.openai.com/api/docs/bots)
- [OpenAI developer docs: commerce key concepts](https://developers.openai.com/commerce/guides/key-concepts)
- [OpenAI developer docs: commerce, get started](https://developers.openai.com/commerce/guides/get-started)
- [Stripe docs: Shared payment tokens](https://docs.stripe.com/agentic-commerce/concepts/shared-payment-tokens)
- [Stripe docs: Machine Payments Protocol](https://docs.stripe.com/payments/machine/mpp)
- [x402](https://www.x402.org)
- [Adyen docs: Network tokenization](https://docs.adyen.com/online-payments/network-tokenization)
- [Visa: Trusted Agent Protocol](https://developer.visa.com/docs/trusted-agent-protocol)
- [Visa: Intelligent Commerce](https://www.visa.com/en-us/solutions/intelligent-commerce.html)
- [Mastercard: Agent Pay (29 April 2025)](https://newsroom.mastercard.com/news/press/2025/april/mastercard-unveils-agent-pay-pioneering-agentic-payments-technology-to-power-commerce-in-the-age-of-ai)
- [Google Merchant Center Help: What is Merchant Center?](https://support.google.com/merchants/answer/188924?hl=en)
- [Google Merchant Center Help: checkout with UCP](https://support.google.com/merchants/answer/16837055?hl=en)
- [Google: Introduction to structured data markup](https://developers.google.com/search/docs/appearance/structured-data/intro-structured-data)
- [Google: AI features and your website](https://developers.google.com/search/docs/appearance/ai-features)
- [Google: Universal Cart (15 October 2026)](https://blog.google/products-and-platforms/products/shopping/universal-cart-launch/)
- [Google: agentic checkout (13 November 2025)](https://blog.google/products-and-platforms/products/shopping/agentic-checkout-holiday-ai-shopping/)
- [schema.org Product](https://schema.org/Product)
- [BigCommerce Support: Guest Customers and Checkout](https://support.bigcommerce.com/articles/Public/Guest-Customers-and-Checkout)
- [Microsoft Advertising: Copilot Checkout (8 January 2026)](https://about.ads.microsoft.com/en/blog/post/january-2026/conversations-that-convert-copilot-checkout-and-brand-agents)
- [Perplexity Help Center: What is Instant Buy?](https://www.perplexity.ai/help-center/en/articles/10352906-what-is-instant-buy)
- [Amazon: Buy for Me](https://www.aboutamazon.com/news/retail/amazon-shopping-app-buy-for-me-brands)
- [Cloudflare blog: the agentic web (30 September 2026)](https://blog.cloudflare.com/agentic-web)
- [Cloudflare blog: the Agent Readiness score](https://blog.cloudflare.com/agent-readiness/)
- [specification.website: Agent readiness overview](https://specification.website/spec/agent-readiness/agent-readiness-overview/)

Last checked 4 Nov 2026