Errors

All error responses share one shape:

{ "error": "human-readable message" }

Status codes

Status	Meaning
400	Malformed or missing request fields
401	Invalid or missing API key
404	Resource not found (e.g. unknown session)
409	Conflict (e.g. session already used)
410	Gone (e.g. session expired)
429	Rate limit or monthly quota exceeded
502	Upstream failure (e.g. Pi Platform API or your callback_url unreachable)

See each endpoint's page for the specific errors it can return: /verify/init, /verify/status.