MCP vs ACP: product discovery and checkout

What each protocol does

MCP stands for Model Context Protocol. ACP here means Agentic Commerce Protocol, not other protocols that share those initials. Choose based on the client and the workflow you need, then check the current specification and the capabilities of your implementation.

Use MCP to call catalog tools

A Siroua MCP client can call search_products, get_product, create_checkout and get_order. It can start with a shopper’s sentence, inspect exact variant details and follow the response’s next action.

This is useful when you control a compatible agent client or integration. Exposing the endpoint is only one half of the connection: the client still needs the URL, authentication and permission to call the tools.

Use ACP to manage a checkout session

A session gives a client a way to prepare a cart, update buyer or shipping information, inspect totals and complete a purchase. In Siroua, completion uses the session ID as the checkout idempotency key, so retries of that session reuse the same intended purchase.

The brand’s own Stripe account receives payment in either access path. Selecting ACP does not change who the merchant is, and protocol support alone is not an approval to join a platform’s consumer shopping program.

Keep business rules consistent across both

The same product should have the same price and checkout checks whichever connection you use. Siroua’s MCP, ACP and REST endpoints share that code rather than each having their own checkout implementation.

Test a changed price, an unavailable variant and a retried payment. Following the protocol is only part of the job; the order also needs to match the catalog and what the shopper agreed to buy.

Choose what your client supports

Use MCP when your client needs catalog tools. Use ACP when the client expects that commerce session interface. Use REST for a custom integration that does not need either protocol. Start with website handoff when you want product discovery without configuring API payments.

Check the current official specs alongside your deployed API schemas. Protocols evolve; this guide describes Siroua’s present workflow rather than claiming every client implements it identically.

References

• Model Context Protocol documentation
• Agentic Commerce Protocol