Codat vs FreeAgent API

Codat

Public OpenAPI specs, an Idempotency-Key header on writes, Retry-After on 429 and a written three-month deprecation notice suit an agent that retries. Access is the limitation. No price or self-serve signup is published, the general Accounting API is closed to new clients, and API keys carry no scopes.

FreeAgent API

Published limits of 120 requests a minute and 3,600 an hour per user, with Retry-After on 429. No OAuth scopes, so a token can do anything the authorising user can.

Codat

1. Send Authorization: Basic <base64 of the API key> to https://api.codat.io. The Portal shows the ready-made header value
2. Send a new GUID as Idempotency-Key on every POST and PATCH, and reuse the same key when retrying after a 429
3. Treat writes as asynchronous on most APIs. Keep the push operation key and wait for the {dataType}.write.successful or .unsuccessful webhook
4. Call the Get model (options) endpoint for the connection before a create or update, because required fields differ by accounting package
5. Filter with query=modifiedDate>... and keep pageSize at 100. The daily quota is 1,000 requests times one plus the number of active connected companies

FreeAgent API

1. Store the new refresh token from every refresh response. The old one stops working
2. Create the invoice, then PUT /v2/invoices/:id/transitions/mark_as_sent. A draft isn't visible to the customer
3. Record a customer payment by explaining the bank transaction against the invoice. There's no invoice payments endpoint
4. Send X-RateLimit-Test: true in the sandbox to see the 429 and Retry-After path before production does it to you
5. Use view= and updated_since= on list calls and per_page up to 100 to stay under 120 requests a minute