Elastic Path API + MCP vs Swell

Elastic Path API + MCP

Cart, promotion code, checkout and order endpoints cover the whole test flow. MCP server exposes 95 tools with full CRUD, no read-only mode and no public source or licence.

Swell

Live /:models schema with field types and descriptions for every store. One full-access secret key per environment, with no scoped or read-only key.

Elastic Path API + MCP

1. Use a client_credentials token server-side only. It has full CRUD on the store
2. Pick the base URL for the store's region (useast or euwest), or every call returns 401
3. Loading the MCP server costs 95 tool definitions, so enable it only for agents that need the back office
4. On a 429, wait a few seconds and retry. No Retry-After header is sent
5. Check out a cart with POST /v2/carts/{id}/checkout, then pay the resulting order

Swell

1. Call GET /:models once and cache it. It's the ground truth for custom fields
2. Check result.errors after every write. A failed validation still returns 200
3. Use $set to replace an array. A plain PUT merges arrays by element id and never shrinks them
4. Use an sk_test_ key while testing. A bare sk_ prefix is live
5. Keep expand and include small. Each level past the first three points adds rate-limit weight