I take that MusicKit JS is built with TypeScript, based on the attributions in the script: https://js-cdn.music.apple.com/musickit/v3/musickit.js In the script it points to https://js-cdn.music.apple.com/musickit/v1/acknowledgements.txt – I assume this should be the v3 URL for the v3 version? It returns the same content nonetheless. This contains attributions for TypeScript. Currently there's a third-party effort with DefinitelyTyped, which publishes the NPM package @types/musickit-js. The latest supported version available is v1. However, there is no version compatible with v3. This makes it hard to use MusicKit JS v3 in a TypeScript project. Please publish the types, ideally on the CDN along with the musickit.js file. Also consider publishing an officially Apple supported DefinitelyTyped package, or help to maintain the existing @types/musickit-js to make consuming this even easier.