The documentation shows the following payload:

{
  "messages": [
    {
      "instance_ptr": "#/traits/foo/bar", # Indicates the field where there is an error.
      "messages": [
        {
          "id": 123, # Unique numeric ID of the error that helps the frontend to interpret this message.
          "text": "field must be longer than 12 characters",
          "type": "validation",
          "context": {
            "value": "short value"
          }
        }
      ]
    }
  ]
}

Currently instance_ptr, messages[].id|text|type are required right?