Agentic Commerce Protocol Guide: ACP vs UCP vs MCP (2026)
An agentic commerce protocol gives software a defined way to exchange business information and perform supported transaction steps. The useful question is which operation your business needs to expose and which clients will use it.
ACP, UCP and MCP have different scopes. Keep the protocol’s capabilities separate from the particular operations your integration implements.
01 Separate discovery, checkout and tool access
| Task | What the integration provides |
|---|---|
| Discovery | Products, availability and relevant offer information |
| Checkout | A supported purchase flow with buyer selections and payment handling |
| Tool access | Callable operations that expose configured business capabilities |
A business can support more than one interface over the same sources. Decide which system owns each fact and action before connecting it.
02 ACP and the purchase flow
The Agentic Commerce Protocol defines a programmatic exchange among buyers, agents and sellers. Its checkout API supports a session lifecycle. The implemented capability of a specific adapter can be narrower than the full protocol.
Evaluate any ACP adapter by its current documented operations and version. A feed connection is not evidence that a complete checkout flow is configured.
03 UCP and configured commerce operations
Configure a UCP integration’s catalog and checkout-handoff operations from its documentation. Connect the catalog to current business data and test the handoff with the merchant’s destination flow.
Check the response, required inputs and supported version. A discoverable endpoint is useful when the downstream operation works with the customer’s selected offer and current permissions.
04 MCP and business tools
MCP provides an interface for tools and resources. In a commerce integration, a tool can expose a catalog or inventory lookup. Its name alone does not define payment, purchase authority or every other transaction behavior.
Describe each tool’s inputs and results, and keep access appropriate to the data or operation. A public product lookup and a private order action need different authority.
05 Build a dependable integration
- Select the client and business operation.
- Read the current adapter’s documented inputs and version.
- Connect the authoritative catalog, policy and payment systems.
- Test successful requests, changed inventory, invalid input and unavailable operations.
- Record the action and outcome so the business can reconcile it.
- Review compatibility when upgrading the adapter or protocol.
06 Use the business information across interfaces
The same source can supply a page, a Markdown response and an adapter when each is configured. This reduces duplicate maintenance and helps keep offer details consistent.
Rebilder’s Console helps the team inspect reported requests and missing answers. Use the activity to select the next useful operation instead of implementing a protocol only because its name is popular.
07 Put the guide to work
Frequently asked questions
What is an agentic commerce protocol?
A defined interface for exchanging business information and carrying out supported commerce operations between participants.
Does ACP support checkout?
The protocol includes a checkout lifecycle. Check which operations the adapter you deploy actually implements and configure the complete flow.
Is MCP a payment protocol?
MCP exposes tools and resources. Payment behavior depends on the specific tool and commerce integration.
Should I support all three?
Choose by the operations and clients your business needs. They can share sources while retaining distinct configuration and authority.