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Protocols for agent commerce: who pays for you, and how

This is a live Practicum page for Volume 2. Verified: 2026-08-18. This field changes every month, so check the date. It supports Chapter 6 of Volume 2, "When the Customer Is Not Human." This page maps the protocols that AI agents use to search, choose, buy, and pay. The book explains the principle. This page holds the current details and links.

Warning: this is a frontier layer that becomes outdated quickly. Check forecast figures in the primary source, such as a company report, McKinsey, or Gartner. Treat vendor statements as claims, not established facts.

Checkout used to be a page completed by a person. Now it can be a protocol that lets an agent complete a purchase without opening that page. A business that these protocols can read is available to this new buyer. A business they cannot read may become invisible to the market by 2030.

Global protocols

The three that matter sit on different parts of one transaction: finding and building the cart, completing the checkout, and proving who authorized the payment. They are layers, not rivals.

Protocol Organization and date What it does Status, Aug 2026
MCP (Model Context Protocol) Anthropic, Nov 2024 connects an agent to tools and data; a de facto foundation Donated to the Linux Foundation; supported by all three large clouds
UCP (Universal Commerce Protocol) Google and Shopify, announced Jan 11, 2026 discovery and cart: how an agent finds a product and assembles an order Open since Jun 17, 2026: any developer can register an agent profile in Shopify's Developer Dashboard without approval. Etsy, Wayfair, Target, and Walmart named as co-developers
ACP (Agentic Commerce Protocol) OpenAI and Stripe, Sep 29, 2025, Apache 2.0 checkout execution inside a conversation The protocol is alive; the flagship product using it is not. See the note below
AP2 (Agent Payments Protocol) Google, donated to the FIDO Alliance Apr 28, 2026 proves that a human actually authorized this agent to spend Now governed by a standards body rather than one vendor
MPP (Machine Payments Protocol) Stripe and Tempo, Mar 2026 machine-to-machine payments between agents and services Early

Payment processors have stopped picking sides. PayPal supports both ACP and UCP and describes them as parallel standards; Stripe, Adyen, and Checkout.com support both. Smaller processors often support only one, which is worth checking before you build.

The most useful thing that happened: the first in-chat checkout failed

OpenAI launched Instant Checkout in ChatGPT on Sep 29, 2025 and pulled it on Mar 4, 2026, after roughly five months. The reason was not a technical failure. People used ChatGPT to research and compare, then finished the purchase on the retailer's own site. Only about a dozen Shopify merchants had integrated it, and Walmart measured checkout inside ChatGPT converting roughly three times worse than a click through to walmart.com.

The protocol survived; the consumer product did not. The industry conclusion has a name now: discover in AI, buy on site. OpenAI shifted toward merchant-controlled checkout, where the agent handles discovery and intent and the merchant keeps the final payment step.

This is the single most useful fact on this page, because it cuts both ways. The agent layer is real and worth preparing for. The specific prediction that people would finish payments inside a chat window was tested in public and lost. Treat any launch date on this page as a pilot until conversion data exists.

The card networks

The protocols above move the order. Someone still has to carry the money and the liability, and that is where the card networks positioned themselves.

Rail Organization What it does
Visa Intelligent Commerce Visa issues an agent a credential tied to a real cardholder, with spending limits set in advance
Mastercard Agent Pay Mastercard agent-initiated payments with a registered agent identity; first live agentic transaction completed in Hong Kong in 2026

The pattern is the same in both: the agent never holds your card. It holds a limited, revocable permission that the network can trace back to a person. That is the practical answer to "who is responsible when an agent buys the wrong thing."

One market outside the US and EU: Russia

Agent commerce is not only being built by American companies, and the non-Western rails are worth watching because they make different bets. Russia is the clearest example with public dates.

Protocol or company Organization and date What it does
YCP (Yandex Commerce Protocol) Yandex, launched Feb 27, 2026 agent commerce inside the Yandex ecosystem; Yandex predicts that agents will handle about 10% of online transactions by 2030, worth more than RUB 3 trillion. This is the company's claim.
GigaNetwork Sber, announced publicly by Alexander Vedyakhin at SPIEF supports agent-to-agent deals backed by bank guarantees; check the primary source for exact wording and current availability

The bank-guarantee angle in GigaNetwork is the interesting part, and it is not the Western design. US and EU rails put the trust question on identity and revocable permissions. This one puts it on a bank standing behind the deal. Which approach holds up is an open question, not a settled one.

What is at risk, and why businesses should care

When an agent chooses and pays, a marketplace can lose two sources of income at once: paid placement, because the agent can ignore sponsored positions, and impulse purchases, because it does not browse a storefront for fun. There is a useful twist. A niche shop or brand may get another chance if it describes its offer in terms an agent can read. The agent can choose based on the product itself instead of an ad bid. Russian market figures from Wildberries, Ozon, ARIR, and VCIOM are in the internal book research card agentic-commerce-marketplaces-ru.

What to do now

  • Use the "Can an agent find me?" checklist to test whether agents can find, evaluate, and complete a transaction with your offer.
  • Start with a machine-readable product or service description, a clear price, and clean examples. An agent needs to understand the offer and act on it without a negotiation.

Update rule: review every month and add a date to outdated information. Version: 2026-08-18.

Sources (verified 2026-08-18)

Primary sources for protocols and payment rails:

Launch dates come from press releases. Keep a pilot separate from general availability.

Protocols for agent commerce: who pays for you, and how