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The base URL is https://api.fastcac.com/v1. Authenticate with your API key as a bearer token:
  • Requests and responses are JSON, except document uploads (multipart) and the certificate and status report (PDF).
  • Every response has a FastCAC-Request-Id header.
  • Errors share one format.
  • Send an Idempotency-Key on POSTs.
  • Lists paginate with limit and starting_after.
  • Ids are prefixed with their type: reg_, biz_, doc_, evt_, we_, org_, key_.
  • Timestamps are UTC, in ISO 8601 with a Z.
The machine-readable spec is at https://api.fastcac.com/v1/openapi.json.