Bad Request v Unprocessible Entity

Case study: GitHub API

https://docs.github.com/en/rest/overview/resources-in-the-rest-api#client-errors

Maybe copying from well known APIs is a wise idea:

There are three possible types of client errors on API calls that receive request bodies:

Sending invalid JSON will result in a 400 Bad Request response:

HTTP/1.1 400 Bad Request
Content-Length: 35
{"message":"Problems parsing JSON"}
Sending the wrong type of JSON values will result in a 400 Bad Request response:

HTTP/1.1 400 Bad Request
Content-Length: 40

{"message":"Body should be a JSON object"}
Sending invalid fields will result in a 422 Unprocessable Entity response:

HTTP/1.1 422 Unprocessable Entity
Content-Length: 149

{
  "message": "Validation Failed",
  "errors": [
    {
      "resource": "Issue",
      "field": "title",
      "code": "missing_field"
    }
  ]
}