Commerce Layer API + MCP vs Ecwid by Lightspeed

Commerce Layer API + MCP

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

Ecwid by Lightspeed

The REST API has 40 access scopes, a published limit of 600 requests a minute per token with Retry-After on a 429, field selection through responseFields, and Markdown docs with an llms.txt index. Tokens never expire, there is no test mode or idempotency key, API access needs a paid plan, and carts are built only in the browser.

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

Ecwid by Lightspeed

1. Send the token as Authorization: Bearer to https://app.ecwid.com/api/v3/{storeId}. Tokens in the query string stopped working in March 2025
2. Use the secret token server-side only. The public token reads enabled products and places orders that are not marked paid
3. Add responseFields, for example total,items(id,name,price), to keep responses small, and page with offset and limit (maximum 100)
4. Stay under 600 requests a minute per token and wait the Retry-After seconds on a 429. Repeated calls with a bad token get the token and IP blocked for longer
5. Work in a separate test store. There is no test mode, and POST /orders writes a real order with no idempotency key
6. After changing an app's scopes, uninstall and reinstall it, then replace the stored tokens. The old ones stop working