Commerce Layer API + MCP vs Vendure

Commerce Layer API + MCP

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

Vendure

Full cart, coupon, shipping and payment flow in the GraphQL Shop API, with ErrorResult types an agent can branch on. No vendor-hosted API. Vendure Cloud is only partly available.

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

Vendure

1. Keep the session token from the first Shop API response and send it on every call. It holds the active order
2. Check each mutation result's __typename and errorCode. Expected failures return 200 with an ErrorResult
3. Don't retry addItemToOrder blindly. Read the active order first, since a repeat adds the quantity again
4. For server-side work, enable api-key in authOptions.tokenMethod and give the key one role in one channel
5. Run 3.7.3 or later, and purge old job records, which may still hold session tokens