HTTP status codes

Code	Meaning
`200`	OK — query or update successful.
`201`	Created — resource created.
`400`	Bad request — malformed JSON, invalid list or invalid `status` filter.
`401`	Unauthorized — missing or invalid API key.
`403`	Forbidden — API access disabled or module capability disabled.
`404`	Not found — subscriber does not exist.
`413`	Payload too large.
`415`	Unsupported media type — use `application/json`.
`422`	Validation error — field-level errors.
`429`	Rate limit exceeded or temporary lockout.

See Response format for the error envelope, and Rate limits for the 429 payload.