API errors

validation_failed

One or more fields failed validation. The `errors` array lists each field and what is wrong with it.

400application/problem+json

What it means

The request parsed, but one or more values in it are not valid. Alongside the standard fields, the body carries an errors array with one entry per failing field: field names the property and detail the rule it broke.

400 · application/problem+json

{
  "type": "https://developers.firsty.app/errors/validation_failed",
  "title": "Validation failed",
  "status": 400,
  "detail": "Request contains invalid fields",
  "code": "validation_failed"
}

How to handle it

Read errors[] rather than the top-level detail, which is a generic summary.
Fix the named fields and resend. The same request fails the same way until it changes, so do not retry automatically.
Check a value's format on the endpoint's reference page when it looks right to you.

Errors reference