Status 400

unsupported_format

This format is not offered here

Why it happens

A .csv or .ics path reached an endpoint with no such form. Most endpoints have no route for a suffix at all, so the same mistake often answers validation_failed or not_found instead.

What to do

Drop the suffix for JSON. The endpoint's Formats line says which forms it answers in.

Example

400 · application/problem+json

{
  "type": "https://unique.domains/api/problems/unsupported_format",
  "title": "This format is not offered here",
  "status": 400,
  "detail": "/names/{name} has no .csv form.",
  "instance": "/v1/names/harbor.io",
  "code": "unsupported_format"
}