PlayerEx is a Minecraft mod built using the Fabric ecosystem that adds RPG themed attributes to the game and the player. It is available to download from Curseforge and Modrinth.
In addition to attributes, PlayerEx adds a levelling system and skill points to spend, enabled through a nonintrusive vanilla-styled gui accessible from the inventory or by hotkey. For further documentation, as well as how to use the PlayerEx API in your own project, please see the wiki.