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ACP, AP2, MCP: the protocol race, in plain English
Three acronyms decide how AI agents will buy things. Here's what each one actually does — and what a merchant genuinely needs to know.
NeuralPay · 28 May 2026 · 6 min read
Every platform shift has a protocol race. The web had browsers vs. proprietary networks; payments had EMV; this one has a small pile of acronyms. If you sell online, you don’t need to implement any of them — but you should know what they are, because they decide which stores AI assistants can buy from.
ACP — the checkout rails
The Agentic Commerce Protocol, developed by OpenAI with Stripe, is the spec behind “Buy it in ChatGPT.” It defines how an agent presents a purchase to a merchant: what a product offer looks like, how the order is proposed, how payment is delegated securely so the agent never holds raw card numbers.
If you remember one thing: ACP is how ChatGPT — the assistant with the largest head start in shopping — completes an order. It’s open-source, and it’s live in production in the US.
AP2 — the payment mandate
Google’s Agent Payments Protocol attacks a harder, narrower question: how do you prove the human said yes? AP2 wraps each purchase in a signed mandate — cryptographic evidence chaining the customer’s instruction to the agent’s action to the payment. When disputes happen (“I never ordered this!”), the mandate is the receipt.
Banks and card networks care enormously about this, which is why AP2’s partner list reads like a payments industry conference badge wall. Where ACP moves the order, AP2 makes the order defensible.
MCP — the plumbing underneath
Anthropic’s Model Context Protocol isn’t about commerce at all — it’s the general standard for connecting AI models to external tools and data, adopted across the industry. It matters here because it’s frequently the transport layer through which an agent talks to anything, including catalogues and checkouts. Think of it as USB: not a shopping technology, but the port shopping technology plugs into.
Who wins?
Probably nobody, and that’s fine. The realistic outcome — the one the last thirty years of infrastructure history suggests — is coexistence: ChatGPT traffic arrives via ACP, mandate verification leans on AP2, tool connections ride MCP, and regional players add their own dialects. The browser wars ended with everyone speaking HTML; the agent wars will end with every serious store speaking several of these at once.
Which is exactly the merchant’s problem. Nobody running a store has time to track three living specifications, their version bumps, their key rotations and their regional quirks. You didn’t implement TCP/IP to get a website either — you got hosting.
That’s the entire reason NeuralPay exists: we speak the protocols so merchants don’t have to. One install, and whichever standard the next big assistant bets on, your store already answers.