| 400 | Bad Request | The body of the request invalid. The request must be changed before being retried. |
| 404 | Not Found | The requested resource could not be found. The request must be changed before being retried. |
| 422 | Unprocessable Entity | The request body is valid, but lacks a pre-condition. This request should be retried eventually, but retrying it immediately will yield no progress. |
| 500 | Internal Server Error | The server encountered an error while processing the request. This request should be retried without change. |
| 400 | Bad Request | The body of the request invalid. The request either must be changed before being retried or depends on another request being processed before it. |
| 404 | Not Found | The requested resource could not be found. The request must be changed before being retried. |
| 422 | Unprocessable Entity | The request body is valid, but unsupported. This request should never be retried. |
| 500 | Internal Server Error | The server encountered an error while processing the request. This request should be retried without change. |