By default, every tool and weapon in the game displays its Attack Damage and Attack Speed attributes in green text, and their values are displayed 1:1 with their actual attribute values (i.e; the unenchanted Shovel in the screenshot shows "2.5 Attack Damage", which is exactly how much damage it deals).

However, when any custom attributes are applied to a tool via commands or datapacks, all of its attributes change format; instead displaying as blue or red, and presenting their attributes in relativity to the player's base stats (i.e; the unenchanted Ancient Wooden Shovel shows "+1.5 Attack Damage", rather than the flat 2.5 displayed on the default Wooden Shovel).

This change alone makes it extremely confusing to compare tool stats between Vanilla and modified tools, but it gets worse when you enchant them; while enchantment buffs do get displayed on unmodified tools' tooltips (note that the enchanted default Wooden Shovel shows "5.5 Attack Damage"), they do not display on modified tools — the Sharpness V Ancient Wooden Shovel seen in the screenshot does not indicate anywhere that it has gained a damage buff from its enchantment, despite the fact that it does indeed deal significantly more damage.

This inconsistency is super frustrating, both from a map-maker perspective, and from a player's perspective. For the player, this makes it super unintuitive to figure out how good a custom weapon actually is, as the tooltip makes it look like any custom weapon is significantly worse than its vanilla counterpart, even if the stats are actually much better in practice. And for map makers, this makes it really difficult to figure out if you've actually set your item up correctly, as the UI flat-out lies to you about what's really going on.

I could see this being addressed a few different ways; either fix the implementation of custom tooltips so it displays enchantment buffs properly, or add some sort of tag to determine whether the item should display its attributes using the default display method, or if it should alter them to make its presentation more like that of vanilla tools'.

Below are some screenshots showcasing the differences between four different items; an unenchanted vanilla Wooden Shovel, a Sharpness V vanilla Wooden Shovel, an unenchanted "Ancient" Wooden Shovel created via datapack, and a Sharpness V version of the same shovel.