{
  "id": "http://yourdomain.com/schemas/myschema.json",
  "description": "Example description",
  "type": "object",
  "properties": {
    "first_name": {
      "type": ["string", "null"]
    },
    "last_name": {
      "type": ["string", "null"]
    }
  },
  "required": ["first_name"],
  "additionalProperties": false
}