---
title: "Create Cart Metafield"
description: "Use POST /carts/{cart_id}/metafields to create a cart metafield. The current public operation is CartMetafield.register."
canonical: https://docs.ordering.co/api-reference/guides/create-cart-metafield/
---

# Create Cart Metafield

> **API operation:** [Open the endpoint in the API reference](https://docs.ordering.co/api-reference/#tag/carts/POST/carts/{cart_id}/metafields)

Use `POST /carts/{cart_id}/metafields` to create a cart metafield. The current public operation is `CartMetafield.register`.

If available, the operation allows authenticated roles `0`, `2`, and `5`; ordinary cross-user access is rejected, and the cart UUID is resolved for the selected user. This is broader than administrator-only access.

Keys beginning with `extra_value` are included in cart-total calculation when their value type is numeric; the `extra_value_` prefix is a narrower naming convention. Consult the API reference and [Extra attributes (Metafields)](https://docs.ordering.co/api-reference/guides/extra-attributes/) for current fields and value types.

## OpenAPI reference

**Operation:** `POST /carts/{cart_id}/metafields`

**Path parameters**

| Name      | Type   | Required | Description |
| --------- | ------ | -------- | ----------- |
| `cart_id` | string | Yes      | —           |

**Header parameters**

| Name            | Type   | Required | Description |
| --------------- | ------ | -------- | ----------- |
| `X-SOCKET-ID-X` | string | No       | —           |

**Request body fields**

| Name         | Type    | Required |
| ------------ | ------- | -------- |
| `model`      | any     | Yes      |
| `object_id`  | integer | Yes      |
| `user_id`    | any     | No       |
| `value`      | any     | Yes      |
| `value_type` | string  | Yes      |

**Responses**

| Code | Description                           |
| ---- | ------------------------------------- |
| 200  | OK (Envelope)                         |
| 400  | Bad Request (ErrorResponse)           |
| 401  | Unauthorized                          |
| 404  | Not Found                             |
| 429  | Too Many Requests (ErrorResponse)     |
| 500  | Internal Server Error (ErrorResponse) |
| 503  | Service Unavailable (ErrorResponse)   |

[Open this operation in the API reference](https://docs.ordering.co/api-reference/#tag/carts/POST/carts/{cart_id}/metafields)