FreshBooks API vs Rutter Accounting API

FreshBooks API

OAuth scopes split read and write per resource, such as user:invoices:read. Rate limits have no numbers, status code or headers.

Rutter Accounting API

Idempotency-Key header on writes, and prefer_sync writes that fall back to async after 30 seconds. Production prices are quote-only.

FreshBooks API

1. Call /auth/api/v1/users/me first and keep both ids. Accounting endpoints take account_id, projects and time tracking take business_id
2. Serialise token refreshes. Issuing a new refresh token kills the old one at once
3. Mark an invoice as sent (action_mark_as_sent) or email it. Reports ignore drafts
4. Send x-api-version: 2023-09-25 on journal entry calls
5. Back off on any throttling response yourself. There's no Retry-After to read and no published limit

Rutter Accounting API

1. Send X-Rutter-Version: 2024-08-31 on every call
2. Send an Idempotency-Key on every create so a retry after a timeout doesn't write twice
3. Use response_mode=prefer_sync and handle the 202 async_response anyway
4. Treat 452 as the ledger throttling you and 429 as Rutter's 500-per-10-seconds organisation limit
5. Keep access_token out of logged URLs. The docs only show it as a query parameter