Status 400
validation_failed
A value is not valid
Why it happens
A value in the path or the query is not one the endpoint takes: a bare word where a domain name belongs, an ending the catalog does not hold, a date in the wrong form, a limit that is not a positive integer.
What to do
Read detail, which names the value, and send it in the form the endpoint's request table gives. A refused domain name adds reason, and suggestion when there is a likely name.
Example
{
"type": "https://unique.domains/api/problems/validation_failed",
"title": "A value is not valid",
"status": 400,
"detail": "A bare word is not a domain name: add its ending (`example.com`).",
"instance": "/v1/names/harbor",
"code": "validation_failed",
"reason": "not_a_name",
"suggestion": null
}