Fabric vs Swell

Fabric

Public OpenAPI files for about 980 operations, llms.txt, client credentials with role-limited system apps, and a published 99.9 per cent SLA. Access needs a sales contract, with no public price or self-serve trial. The commerce docs are labelled legacy, the newest release notes date from July 2025, and no status page was found.

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.

Fabric

1. Get the tenant ID and a System App client ID and secret from the merchant's Copilot admin, with the narrowest role the task needs
2. Request a new system token from {authURL}/v1/token every 10 minutes, since system apps receive no refresh token
3. Send x-fabric-tenant-id on every call, and x-fabric-channel-id where the merchant sells in more than one channel
4. Page order searches with offset and limit, because the default response returns 10 orders
5. Read errorCode and context.endpoint in Orders and Inventory errors, and check for duplicates before retrying a write

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