Resources

The ACP specification site: checkout sessions, carts, feeds and delegated payment between an agent and a merchant.

www.agenticcommerce.dev/

OpenAPI documents, JSON Schema and markdown RFCs, versioned by date. Apache-2.0.

github.com/agentic-commerce-protocol/agentic-commerce-protocol

Stripe's implementation guide — agentic checkout, cart and feed, delegated payment and authentication, orders and webhooks — and the page that names Stripe, OpenAI and Meta as ACP's authors.

docs.stripe.com/agentic-commerce/acp

Open protocol for agent commerce covering catalog, cart, checkout and order lifecycle. Apache-2.0.

ucp.dev/

The UCP spec and docs, with SDKs and a conformance suite.

github.com/Universal-Commerce-Protocol/ucp

Shopify's agent surface built on UCP: global and storefront catalogs, universal cart, cart and checkout MCP servers, order webhooks.

shopify.dev/docs/agents

Merchant-facing guides and specs for selling inside ChatGPT: product feeds, agentic checkout, delegated payment, promotions.

developers.openai.com/commerce

Shopify's engineering write-up of why UCP exists and how it is put together.

shopify.engineering/UCP

Specification for agent-initiated payments built on signed mandates: intent, cart and payment, for human-present and autonomous flows.

ap2-protocol.org/

Python SDK, samples and a web client for the AP2 mandate flow. Apache-2.0.

github.com/google-agentic-commerce/AP2

The launch post, with the reasoning behind mandates and the list of launch partners.

cloud.google.com/blog/products/ai-machine-learning/announcing-agents-to-payments-ap2-protocol

An HTTP-native payment standard that revives 402 Payment Required: a server answers with terms, the client pays and retries.

x402.org/

How the scheme works end to end, with client and server implementations.

docs.x402.org/introduction

The main implementation, now under the foundation. TypeScript.

github.com/x402-foundation/x402

Stripe's agent documentation: an MCP server, agent plugins and skills, and how to accept payments from agents.

docs.stripe.com/agents

The launch announcement, and the clearest description of shared payment tokens scoped to a merchant and cart total.

stripe.com/newsroom/news/stripe-openai-instant-checkout

Visa's programme for agent-bound tokenized credentials, with controls and signals for merchants.

www.visa.com/en-us/solutions/intelligent-commerce

The developer view: tokenization, authentication, payment instructions and signals, with a sandbox.

developer.visa.com/capabilities/visa-intelligent-commerce

PayPal's merchant documentation for accepting payments initiated by an assistant.

developer.paypal.com/agent-ready/overview

PayPal's wider agentic service set for merchants and platforms.

developer.paypal.com/agentic-commerce-services/about

The protocol for giving a model tools and data. Commerce reaches it through other specs: ACP defines an MCP binding, UCP an MCP transport.

modelcontextprotocol.io

The current dated specification. There is no official commerce or payments extension.

modelcontextprotocol.io/specification/2026-07-28

The official extension index: apps, authorization, tasks and skills.

modelcontextprotocol.io/extensions/overview

Open standard for agents talking to other agents, donated by Google to the Linux Foundation.

a2a-protocol.org/latest/

The x402 payment extension for A2A: one agent pays another for a service, on chain.

github.com/google-agentic-commerce/a2a-x402

The vocabulary behind product markup: price, availability, identifiers. Old, boring, and what most crawlers already read.

schema.org/Product

A convention for a short markdown brief at a fixed path, aimed at models rather than crawlers.

llmstxt.org/

Turns a site into a conversational endpoint that is also an MCP server, answering in schema.org JSON. Moved from the microsoft org.

github.com/nlweb-ai/NLWeb

A worked example of a catalogue built for machine buyers, including a per-merchant catalog MCP server.

shopify.dev/docs/agents/catalog

How UCP models catalogues, carts and orders, from the people who built it.

developers.googleblog.com/under-the-hood-universal-commerce-protocol-ucp/

Signed HTTP requests that identify an automated client with a key directory, built on RFC 9421 message signatures.

developers.cloudflare.com/bots/reference/bot-verification/web-bot-auth/

The active IETF group standardising this, with a charter that explicitly covers agents acting for users.

datatracker.ietf.org/wg/webbotauth/about/

The architecture draft: how a bot proves its identity with HTTP message signatures.

datatracker.ietf.org/doc/draft-meunier-web-bot-auth-architecture/

Authenticated agent traffic plus value exchange over HTTP 402 with pluggable micropayments. The closest thing to an IETF agent-payments draft.

datatracker.ietf.org/doc/draft-dhir-http-agent-profile/

Visa's open spec for a merchant to verify an agent's identity and the mandate it is acting under.

github.com/visa/trusted-agent-protocol

Why cryptographic identity beats user-agent strings and IP allowlists for agent traffic.

blog.cloudflare.com/signed-agents/

Charging automated clients per request at the edge, again using 402.

developers.cloudflare.com/ai-crawl-control/features/pay-per-crawl/

Models x402, MPP, ACP and AP2 in Tamarin across 86 verification cases, reporting 40 previously undocumented findings. August 2026.

arxiv.org/abs/2609.00060

Four classes of flaw in deployed x402 integrations that allow resource theft, with mitigations. May 2026.

arxiv.org/abs/2605.30998

A taxonomy of 33 structural protocol vulnerabilities, including payment-hijacking chains, plus a benchmark. July 2026.

arxiv.org/abs/2607.21824

An application profile for refundable, delayed-fulfilment purchases using authorize-and-capture escrow. September 2026.

arxiv.org/abs/2609.02208

Wallets and stablecoin infrastructure with agent-funded wallets, virtual cards and a purchase API.

www.crossmint.com/

Identity and wallet stack for agents: know-your-agent tokens, mandates, and a checkout product.

skyfire.xyz/

Merchant tooling for exposing agent-callable actions on a site, with analytics on how agents use them.

nekuda.ai/

Stripe's AI SDK, token metering, MCP server and agent skills. Moved from stripe/agent-toolkit.

github.com/stripe/ai

A community index of protocols and implementations, useful for spotting what is new.

github.com/xpaysh/awesome-agentic-commerce