not_found

HTTP 404

No such resource, or it is not visible to this caller.

Response shape

{
  "type": "https://cogdepot.com/problems/not_found",
  "title": "<short human-readable summary>",
  "status": 404,
  "detail": "<what happened on this occurrence>",
  "reason": "not_found"
}

Branch on reason. The title is prose and may be reworded; reason is the stable contract.