this was made for the purposes of pulling some files from the game to modify and build a resourcepack from, NOT to download and illegally play Minecraft. You can't play using the downloaded file unless you have a paid Minecraft account (because this is the same file as from the launcher).
Optional (default: latest) The Minecraft version to download (defaults to latest release)
If mcversion is latest or release, the latest release (not snapshot) version is downloaded
If mcversion is latest-snapshot, latest snapshot, or snapshot, the latest snapshot version is downloaded
Otherwise, mcversion is expected to be a version string, like 1.16.3, 1.16.4-pre1, 20w30a, a1.0.4, c0.0.11a or rd132211. (the last 3 are very old versions, so the string may look a little odd)
Optional (default: minecraft-<version>.jar) The name of the file to save to. (if no file extension is provided, it will be set as .jar)
the name of the jar file downloaded (provided for when mcversion is latest, snapshot or similar)
the version of minecraft that was downloaded (provided for when mcversion was set to latest or snapshot)
I don't include that in this action, because essentially the downloaded jar file is just a zip file. You can use unzip or 7z to unzip the resulting file.