Hello Life,
The same functionality as of the CustomerService.getCustomers() in AdWordsAPI is available via
customerClient resource in Google Ads API Beta. You could use the below query to get all the accounts under an MCC. Please let me know if you have any further questions.
Query:
"SELECT customer_client.client_customer, customer_client.currency_code, customer_client.descriptive_name, customer_client.hidden,
customer_client.id, customer_client.level, customer_client.manager, customer_client.resource_name, customer_client.test_account, customer_client.time_zone FROM customer_client"
Regards,
Sai Teja, Google Ads API Team

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