# MODIFIER_REQUIRED

# MODIFIER_REQUIRED

A line item is missing a modifier selection that the catalog marks as required (e.g. a "size" group on a drink, or a "protein" group on a bowl).

*Reserved error code — not currently emitted by any endpoint. Partners may begin handling it defensively; backend will start emitting once wired in.*

## Summary

| Field | Value |
|---|---|
| HTTP status | `400` |
| `errorCategory` | `validation` |
| `retryable` | `false` |

## When This Fires

- **`POST /v1/marketfront/orders/validate`** — a line item references a catalog item whose required modifier group has fewer selections than its `minSelections` value.
- **`POST /v1/marketfront/orders/place`** — same condition reaches placement (typically only possible if validation was skipped).

## Recommended Action

Inspect the catalog modifier groups for the offending item and surface the required selections in your UI:

1. `GET /v1/marketfront/catalog-sets/{catalogSetId}` — find the line item's `modifierGroups[].minSelections`.
2. Prompt the user to satisfy each required group.
3. Resubmit with the populated modifier selections.

The `errors[]` array on the response will pinpoint the offending line item via `jsonPath`.

## Example

```json
{
  "type": "https://developer.gett-tech.com/errors/MODIFIER_REQUIRED",
  "title": "Bad Request",
  "status": 400,
  "detail": "Line item is missing a required modifier selection.",
  "instance": "/v1/marketfront/orders/validate",
  "requestId": "req_abc123",
  "timestamp": "2026-04-27T14:30:00.000Z",
  "errorCode": "MODIFIER_REQUIRED",
  "errorCategory": "validation",
  "retryable": false
}
```