On September 12th, AdWords announced that you can now use one Google login to access multiple AdWords accounts. With this change, you can associate up to 5 AdWords accounts with a single Google account.
To take advantage of this new feature, the AdWords API has changed the behavior of CustomerService.getCustomers() starting with v201603. In the past, the Google account you used to obtain your OAuth2 credentials could only be associated with one AdWords account, which resulted in
Questions? Visit us on the AdWords API Forum or our Google+ page.
Nadine Sundquist, AdWords API Team
To take advantage of this new feature, the AdWords API has changed the behavior of CustomerService.getCustomers() starting with v201603. In the past, the Google account you used to obtain your OAuth2 credentials could only be associated with one AdWords account, which resulted in
getCustomers() only returning one AdWords account. Now that a Google account can be associated with multiple AdWords accounts, getCustomers() can return multiple AdWords accounts. If you only want to retrieve the details of a specific customer using CustomerService, you can set the clientCustomerId in the request header starting with v201607.Questions? Visit us on the AdWords API Forum or our Google+ page.
Nadine Sundquist, AdWords API Team