Minecraft wiki entry for Development_versions, associated text: New trigger: minecraft:item_durability_changed
Triggers when an item in the player's inventory is damaged in some manner, such as hurting a mob with a sword.
Three conditions that can be used for this trigger:
item: Checks information about the item before durability loss.
durability: Checks the durability of the item after durability loss.
delta: Checks how much durability was lost.