An API client sends a request to an API and shows the answer, without a line of code. Postman is the most widely used; Insomnia, Bruno, Hoppscotch or Thunder Client (in VS Code) do the same, with other labels. The steps below use Postman: its labels are those of October 2026, and its interface changes from time to time. In another client, look for the same notions: the method, the URL, the authentication (Basic Auth) and the body.

Prepare a collection

In Postman, a collection groups requests. The authentication is set once on it, and every request added to it uses it.

  1. Create a new collection and choose Blank collection. Name it after your marketplace.
  2. In the collection, open the Authorization tab and choose Basic Auth as the type.
  3. Enter your API key (pk_…) in Username and your API secret (sk_…) in Password, then save the collection.

Send your first request

  1. In the collection, click Add request (or +).

  2. Leave the method on GET and enter the URL of a list, for instance the categories of your listings:

    https://your-marketplace.mykreezalid.com/api/v1/listings/categories

    Replace your-marketplace.mykreezalid.com with your marketplace’s main domain: its custom domain, when one is connected.

  3. Leave the request’s Authorization tab on Inherit auth from parent: it uses the collection’s.

  4. Click Send.

The answer appears below, in JSON: the list of your categories, with the status 200 OK.

Read a seller’s data

Each user has an ID: the number at the end of the URL of their screen in the admin panel, for instance …/admin/users/151155.

In a new GET request of the same collection:

  • …/api/v1/users/151155 returns the user, with their metafields;
  • …/api/v1/users/151155/metafields returns their metafields only.

A metafield is a piece of your own data stored on a user, a listing or an order: a code in your accounting tool, a level, a reference. Each one has a namespace (the group it belongs to), a title (its name) and a value:

{
  "metafields": [
    { "namespace": "crm", "title": "account_code", "value": "V-0042" }
  ]
}

Change a seller’s metafield

  1. In the same collection, add a request and choose POST as the method.

  2. Enter https://your-marketplace.mykreezalid.com/api/v1/users/151155/metafields, with your domain and the seller’s ID.

  3. Leave its authentication on Inherit auth from parent.

  4. Open the Body tab, choose raw, then JSON in the drop-down list on the right.

  5. Paste the metafield:

    { "namespace": "crm", "title": "account_code", "value": "V-0043" }

  6. Click Send.

The answer repeats what was saved. If the user already has a metafield with that namespace and that title, its value is replaced; otherwise it is created. Send the GET request again to check.

To save several at once, send a list: [{ … }, { … }]. For listings and orders, the URL becomes …/listings/<ID>/metafields or …/orders/<ID>/metafields. The developer hub details the metafields.

What your users see

A GET request changes nothing. A POST, PUT or DELETE request changes your marketplace as the admin panel would: a listing created through the API is online for everyone, a user deleted is deleted. Metafields are returned to the user they belong to by the Front API, and a theme can display them: store nothing in them that the user should not see.

Edge cases and limits

  • Real data: Postman acts on your live marketplace. Try your POST requests on a test user or a test listing.
  • Values are text: send "12" rather than 12. A value of "0" or an empty value is refused: use "no" or "-".
  • No deletion: a metafield cannot be deleted through the API; overwrite its value instead.
  • Your theme may read some metafields: changing one can change what the storefront shows. Ask whoever built the theme before you change a namespace you did not create.
  • The other two APIs: this article covers the Admin API only. The Partners API also uses Basic Auth, with a seller’s own credentials; the Front API uses a token obtained by signing in. See Authentication on the developer hub.