AppStore API for search and download?
There are no official API to search the iOS App Store. Also, starting with iTunes 12.7, Apple has removed the ability to browse, search for and download iOS apps on a Mac/PC.

The only currently official way for public users to download and install apps is directly an iOS device via the App Store. This is done as a step towards optimizing the installed app bundle size depending on device type and capabilities.

There is a official iTunes Search API (with very limited support for apps) which you go through and see if meets some of your needs:


iTunes Affiliate Resources