Codat vs Invoice Ninja 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.

Invoice Ninja API

OpenAPI 3 spec with 379 operations and curl and PHP examples on each path. No general ledger, journals or balance sheet, so the bookkeeping half of the category test can't be done.

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

Invoice Ninja API

1. Send X-Requested-With: XMLHttpRequest with X-API-TOKEN on every call
2. Prototype against demo.invoiceninja.com with X-API-TOKEN: TOKEN before asking for real credentials
3. Add ?mark_sent=true to the save to make an invoice live, or ?send_email=true to send it. A plain create is a draft
4. Stay under 1,000 requests a minute per token on the hosted service and 20 a minute on report exports
5. Record a supplier bill as an expense or purchase order. There's no bills resource