Brigadier

"Minecraft tells Brigadier: "These are the things that players can do. Tell me once the player's trying to do this." So when a user types in chat, that goes through Brigadier. Brigadier splits it up, it error checks it, it tries to be as helpful as it can. You’ve also got this lovely pop-up window when you're typing that can suggest what the next bit might be."

- Tom Stone

Brigadier is an open source library for using commands in Java Edition.

Usage
Brigadier is used by the Minecraft game for parsing string commands.