Errors

Failures return JSON { "error": "…" } with a status code.

Status	When	Typical body
`400`	Bad JSON or missing required fields	`missing fields` / `bad json`
`401`	Missing, unknown, or revoked Bearer key	`unauthorized`
`402`	Company billing is locked	`billing locked`
`403`	API disabled, wrong company workspace, or membership / quota	`api disabled` / `forbidden`
`404`	Board or task not found	`not found`
`409`	Dependency block or Google cross-list conflict	Conflict message
`500`	Unexpected server error	Error message