# Metafield definition constraint types

> The catalog of constraint types a metafield definition can use.
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A **Metafield definition constraint type** is one kind of constraint - `category`, `channel`, `category_channel`. Constraints narrow where a [Metafield definition](/api/product-management/metafield-definitions/) applies. This is a **read-only reference** resource.

Constraints depend on the definition's **owner type**, not its data type - and today only the `products` owner type allows any. The authoritative per-owner-type list is the `allowedConstraints` field on [Metafield owner types](/api/product-management/metafield-owner-types/) (see [Type compatibility](/api/product-management/metafield-definitions/#type-compatibility)).

## The Metafield definition constraint type object

## Conventions

All requests require an OAuth 2.0 bearer token:

```
Authorization: Bearer <token>
```

This resource is read-only - it has no create, update or delete operations.