<!-- Extension API v0 — pre-1.0. Interfaces may change without notice until P2 seals the custom-code format. First-party extensions track HEAD. -->

# `metafield.set`

Set a metafield value on a product, variant, collection, or the store.

- **scope**: `catalog:write`
- **storefront-visible** (bumps the catalog generation): yes
- **destructive**: no

## Payload

| field | type | required | notes |
|---|---|---|---|
| `ownerType` | "product" \| "variant" \| "collection" \| "store" | yes |  |
| `ownerId` | string (≤64 chars) | yes |  |
| `namespace` | string (/^(custom\|app\.[a-z0-9-]{2,32})$/) | yes |  |
| `key` | string (/^[a-z0-9_]{1,64}$/) | yes |  |
| `value` | object | yes |  |

### JSON Schema

```json
{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "ownerType": {
      "type": "string",
      "enum": [
        "product",
        "variant",
        "collection",
        "store"
      ]
    },
    "ownerId": {
      "type": "string",
      "minLength": 1,
      "maxLength": 64
    },
    "namespace": {
      "type": "string",
      "pattern": "^(custom|app\\.[a-z0-9-]{2,32})$"
    },
    "key": {
      "type": "string",
      "pattern": "^[a-z0-9_]{1,64}$"
    },
    "value": {}
  },
  "required": [
    "ownerType",
    "ownerId",
    "namespace",
    "key",
    "value"
  ],
  "additionalProperties": false
}
```