I am trying to change attributes like attack damage and attack speed of existing items, but I'm wondering what the best way to do this would be. Right now, I can change the values perfectly fine through creating and setting a new NBTTagCompound to the item. However, I'm wondering if this is the best way to do it, or even if it's the only way. I noticed a few limitations, considering it basically rewrites ItemSword's tooltip in favor of a blue text instead, though, with this, the Attack Speed value displayed isn't necessarily correct. Sword's by default have a -2.4 attack speed modifier, but changing the attributes like I did means the number won't get added to the player's base attack speed (which is 4, which would equal 1.6). The Attack Speed gets correctly set but is instead displayed as a negative number, which can be misleading. I've tried changing the tooltip, but retrieving the value in the attribute is hard to get, and when I do retrieve it, it is always the default -2.4.

 

I feel like I'm not doing this right, but if anyone knows a way around this or has a better way of doing it, I would appreciate it.

Try using attribute modifiers.

That's what I'm doing. Manually adding the NBT data to the item seems to override the default AttributeModifiers, which I think is the only way to do this.

I don't think you need NBT to modify the attributes... I'm not sure, but I do think that this is the only way.