Some operations can only be preformed through the firebase-admin SDK, or sometimes you just want to run/test some Firestore query.

The Firebase CLI can provide a "shell" command that opens a Node.js REPL with the firebase-admin SDK preconfigured and global variables such as "db", "auth" that you can then use to interact with Firebase.

This was so much needed that I implemented this by myself in our project as a custom package.json scripts.