You must supply the app ID in order to use the API to retrieve data. To do this, there are several methods.
On the App Store / Play Store
Look for an app on the web stores and extract the ID from the URL. Example below for the app Facebook.
App Store: extract '284882215' from the URL https://apps.apple.com/us/app/facebook/id284882215
Play Store: extract 'com.facebook.katana' from the URL: https://play.google.com/store/apps/details?id=com.facebook.katana
On AppTweak's tool
Visit an app's page on AppTweak's platform and extract the ID from the URL. Example below for the app Facebook.
App Store: extract '284882215' after /ios/ from the URL https://app.apptweak.com/aso-intelligence/applications/ios/284882215/metadata?scope=country&country=us&language=us&device=iphone&view=aso_report
Play Store: extract '' after /android/ from the URL https://app.apptweak.com/aso-intelligence/applications/android/com.facebook.katana/metadata?country=us&device=android&language=us&scope=country&view=aso_report