Idempotency

Send an Idempotency-Key header on POST requests. If the network drops after FastCAC acted but before you got the answer, retry with the same key and you get the original response back instead of a second registration.

curl https://api.fastcac.com/v1/registrations \
  -H "Authorization: Bearer $FASTCAC_KEY" -H "Content-Type: application/json" \
  -H "Idempotency-Key: order-1182-create" \
  -d '{"external_id": "order-1182", "proposed_names": ["Ada Foods Ventures"]}'

Use a value unique to the operation: a UUID, or your own order id plus the action. Up to 255 characters.
A successful (2xx) response is kept for 24 hours. Retrying with the same key and the same request returns it again, with the header Idempotent-Replayed: true.

The same key with a different request is a 409 idempotency_key_reused:

{
  "error": {
    "type": "idempotency_error",
    "code": "idempotency_key_reused",
    "message": "This Idempotency-Key was used for a different request.",
    "param": null,
    "request_id": "req_ePT5LinP29madPXjGae6SMNT"
  }
}

A retry while the first request is still running gets 409 idempotency_request_in_progress. Wait a moment and retry.
Failed requests aren’t stored, so you can fix the request and reuse the key.
Keys are separate per organization and per mode.

GET, PATCH and DELETE don’t need a key: repeating them has the same effect as sending them once.

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Registering a business

Webhooks

API basics

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