Access levels and RMF
The Google Ads API has access levels associated with the developer token, and uses an application review process to grant various access levels. It's important to plan and obtain the correct access levels before productionizing your application.
A common scenario is that your application development could start off with Basic Access but then outgrow it's quota limits over time. At that point, you'd need to apply for Standard Access. Since the review process could take days or sometimes weeks to complete, request the Standard Access upgrade well before you actually need the increased quota limits.
Google may require that your app provide certain capabilities or features as listed in the Required Minimum Functionality (RMF). When using the Google Ads API, the RMF only applies to developer tokens with Standard Access. Make sure you review these requirements in advance to avoid additional delays around building the necessary features in your app.