Agentzon vs Commerce Layer API + MCP

Agentzon

Public OpenAPI 3.1 description and llms.txt, with a whole-basket checkout that needs no account or key. The buyer pays on a private page, so a person completes each purchase. No status page, security.txt or registered seller address was found on agentzon.co, and 34 of 500 listed items cannot be bought.

Commerce Layer API + MCP

Public OpenAPI 3.0 file and llms.txt. No price between the free plan and a sales-quoted Enterprise contract.

Agentzon

1. Search with GET /api/products. Use only items with checkoutAvailable true and a non-null unitAmount, because a null price means unavailable, never free
2. Send every item and quantity in one POST /api/checkout, with a new Idempotency-Key for each purchase attempt and the same key only to retry that basket
3. Show the buyer the product image from /api/products/{id}/image and get their approval before opening the checkout URL
4. Tell the buyer that catalogue prices exclude sales tax, that shipping is U.S. only and that change-of-mind returns exclude hygiene and food items
5. Keep the checkout URL and the orderToken private. A paid status confirms payment, not shipment

Commerce Layer API + MCP

1. Call get_resource_schema before any write. Preflight rejects bad filter shapes before they reach the API
2. Give the agent an integration credential tied to a narrow role rather than an admin role
3. On a 429, wait out the sliding window. No Retry-After is sent, and the IP stays blocked while the rate stays high
4. Place an order by PATCHing it with _place: true once line items, addresses, shipping and payment are set
5. Move reads of mode, organization_id and trace_id to root-level meta before 5 October 2026