If you’re curious to see whether an app you use has an Apple TV version, or if you just want a one-stop place to grab all available apps, check your Apple TV’s App Store. Under Purchased > Not on This Apple TV, you’ll see Apple TV versions of every app you’ve ever downloaded.
Since they’re all universal purchases—meaning there is (currently) no way to charge separately or extra for the Apple TV version of an app—all apps listed here are free downloads as long as you purchased or downloaded the iPhone or iPad version first.