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OACP — agentic commerce, made safe

What OACP is and why you need it

OACP is one trust layer under UCP, ACP, AP2, Visa TAP, MCP and A2A: your facts stated once, signed, decided by fixed rules and recorded, then rendered into each standard.

Merchants and business owners5 min readReviewed 2026-10-21
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The short version

OACP stands for Open Agentic Commerce Protocol.

It is a safety layer for selling to AI agents. It sits under the agent standards you already hear about. It does not compete with them.

Think of it as one source of truth for your shop. Every agent channel reads from it. Every purchase passes through the same rules. Every decision lands in the same record.

Five copies versus one layer

On the left, each standard is wired on its own, so the shop keeps five sets of facts, keys and logs. On the right, the shop feeds one OACP layer, and adapters render it for every buyer agent.

A shop wired to UCP, ACP, AP2, TAP and MCP separately. Tangled lines lead to five boxes, each holding its own facts, keys and log.Without OACPEach protocol wired on its ownYour shopUCPown factsown keysown logACPown factsown keysown logAP2own factsown keysown logTAPown factsown keysown logMCPown factsown keysown logFive copies to keep in syncThe same shop feeds one OACP layer of signed facts, one rule set, one ledger and one revoke switch. Adapters render it as UCP, ACP, AP2, TAP and MCP for every buyer agent.With OACP underneathOne set of facts, many outputsYour shopOACP layerSigned facts · one rule setOne ledger · one revoke switchUCPACPAP2TAPMCPEvery buyer agentOne copy, the same everywhere

Why sellers need it

AI agents now shop for people. One agent compares prices. Another fills a cart. A third pays.

Each of those steps has its own standard. If you connect to each standard separately, four problems appear:

  • Many sources of truth. A price changes in one feed but not another.
  • Many trust set-ups. Each integration has its own keys and its own checks.
  • Many logs. Nobody can show one clean record of what happened.
  • No common off switch. Pull a product in one place and an agent can still buy it somewhere else.

OACP fixes these by putting one layer underneath. You keep your facts in one place. Every channel reads the same signed copy.

The standards, in one line each

You do not need to learn these. OACP renders into them for you.

Standard What it answers What OACP gives it
UCP (Universal Commerce Protocol) Where is the shop, what does it sell, how do I check out? Your business profile, catalog, checkout and orders
ACP (Agentic Commerce Protocol) Which products can an agent buy, and how? A product feed and agent checkout sessions
AP2 (Agent Payments Protocol) What did the buyer allow the agent to spend? Intent, Cart and Payment mandates, mapped to AP2 field names
Visa TAP and Web Bot Auth Which agent is calling, and is it really that agent? Signature checks on agent requests
Mastercard Agent Pay Which card-network agent id does this agent have? The scheme label, recorded from the registry (its wire details are not public)
MCP and A2A How do agents and tools talk to each other? Checkout tools for MCP clients and a seller agent for A2A

Each standard answers one question

Discovery, checkout, payment permission and agent identity each have their own standard. OACP sits underneath and feeds all of them from the same signed facts.

Five rows of standards: UCP for finding the shop and checking out, ACP for the product feed and agent checkout, AP2 for what the buyer allowed, Visa TAP and Web Bot Auth for which agent is calling, and MCP and A2A for how agents and tools talk. Underneath them sits one OACP layer of signed facts, one rule set and one record, fed by your shop.UCPFind the shop and check outACPProduct feed and agent checkoutAP2What the buyer allowedTAP · Web Bot AuthWhich agent is callingMCP · A2AHow agents and tools talkOACP underneathSigned facts · one rule set · one recordYour shop

What OACP actually is

OACP is three things working together:

  1. Signed facts. Your catalog, prices, stock and policies become small signed records. Grantex signs them. Each one has an expiry date and a revocation slot.
  2. One decision before money moves. A fixed rule set, called the arbiter, says allow or refuse. No allow, no payment.
  3. One record. Every decision and every commerce write is recorded in a signed ledger you can export and check.

Adapters then render those facts into each standard's own format.

Who does what

  1. 1Your shop

    Stays the source of truth for products, prices, stock and orders. Shopify is the supported source today.

  2. 2Grantex

    Signs your facts, publishes the signing keys, runs the revocation list and issues buyer mandates.

  3. 3AgenticOrg

    Checks every signature, decides each purchase with fixed rules, records it and speaks each standard.

  4. 4Payment provider

    Moves money, and only after an allow decision. Plural is the rail built today.

What OACP is not

Honesty matters here, so here is the plain list.

  • Not a replacement. OACP renders into UCP, ACP and AP2. Buyer agents still speak those standards.
  • Not a certification. The groups behind UCP, ACP, AP2 and TAP have not certified or endorsed OACP.
  • Not regulatory approval. OACP helps you keep evidence. It does not establish regulatory compliance on its own.
  • Not AP2's own format. Mandates are signed JWTs that use AP2 field names, not AP2's SD-JWT format. Passkey signing of the cart is a Grantex extension.
  • Not switched on by default. Checkout, payment, mandates and public discovery each sit behind a switch that starts off. See feature switches.

Implementation references

This guide is checked against repository sources. Enabled features and deployed versions may differ by environment.