Minecraft wiki entry for JSON_format, associated text:  conditions:
 items: A list of items in the player's inventory. All items in the list must be in the player's inventory, but not all items in the player's inventory have to be in this list.
:
Tags common to all items[show]
 slots:
 empty: The amount of slots empty in the inventory.
 empty:
 max: The maximum value.
 min: The minimum value.
 full: The amount of slots completely filled (stacksize) in the inventory.
 full:
 max: The maximum value.
 min: The minimum value.
 occupied: The amount of slots occupied in the inventory.
 occupied:
 max: The maximum value.
 min: The minimum value.
 player: The player that would get the advancement. May also be a list of predicates that must pass in order for the trigger to activate.
All possible conditions for entities[show]