If you have an existing Merchant Center account, you can use [Google APIs
Explorer](https://developers.google.com/apis-explorer) in the [reference documentation](https://developers.google.com/merchant/api/reference/rest) to verify
that your account is ready to use with the Merchant API.

1. Find the resource name of your account by concatenating `accounts/` and your `merchantId`. You can find your `merchantId` in the top of [Google Merchant Center](https://merchants.google.com/).
2. In the API Explorer for the [`accounts.products.list`](https://developers.google.com/merchant/api/reference/rest/products_v1/accounts.products/list) method, do the following:
   1. Enter the resource name of your account in the `parent` field.
   2. In the **Credentials** section, select **Google OAuth 2.0** and **API
      key**.
   3. Click **Execute**.
   4. If prompted, sign in with the Google Account associated with your Google Merchant Center account.

If your Merchant Center account is set up correctly, the request succeeds and
returns an HTTP response code `200`. If you just created a new account, the
`accounts.products.list` method doesn't return any products.

Next, try [using a client library](https://developers.google.com/merchant/api/client-libraries) to request
access to other Merchant Center accounts. Client libraries support user
authorization, which grants an application permission to access and manage
Merchant Center account data.

You can also [use a service
account](https://developers.google.com/merchant/api/guides/authorization/access-your-account) to authorize
API access to your own account. A service account is a special type of account
that belongs to an application instead of an individual end user. For more
information, see [Service accounts overview](https://cloud.google.com/iam/docs/service-account-overview).