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This library allows for easy and highly efficient checking for the swapping of equipment

Register an Item

Simply apply the modifier tungsten:apply/<slot> to the item for each slot tungsten should react to. This can be done using the item command or in a loot table as a minecraft:reference function:

item modify entity @s <...> tungsten:apply/<slot>
{ "function": "minecraft:reference", "name": "tungsten:apply/<slot>" }

If you want to give a tungsten-ready item as a crafting reward or somewhere, where you can't use item modifiers, you can add the following component:

"minecraft:attribute_modifiers": {
    "modifiers": [{
            "attribute": "minecraft:generic.luck",
            "name": "tungsten.<slot>",
            "amount": -9.094947017729282e-13,
            "operation": "add_value",
            "id": "<uuid>",
            "slot": "<slot>"
    "show_in_tooltip": false

Make sure to replace <slot> with the slot tungsten should work for and the <uuid> in hex using the following table:

SlotUUID in HexUUID in 4 Values

Register a Function to run when Swapping

The following function tags are executed once for each player, when (and only when) items of this library get equiped, unequiped or swapped.

Function tagExecuted
#tungsten:swap/mainhandwhen changing a mainhand item
#tungsten:swap/offhandwhen changing an offhand item
#tungsten:swap/headwhen changing a head item
#tungsten:swap/chestwhen changing a chest item
#tungsten:swap/legswhen changing a legs item
#tungsten:swap/feetwhen changing a feet item

Add a function from your pack to the function tags, that handles the swapping of that type of equipment.

A function tag could look something like this:


{ "values":[ "your_pack:swap/mainhand" ]}

The functions in the tag are executed as and at the player, so the player can be selected using the @s selector.

[!Note] Previously you could access and modify nbt of the swapped in item through a provided storage, this is no longer possible. Use a predicate to detect if the item is of your pack and then read the nbt you need to access. If this is something you relied on, please let me know of your usecase by opening an issue.

Embedding the Library

To quickly set up this pack, copy the load and tungsten namespace into your pack and add merge the file located at /data/minecraft/tags/functions/load.json.

The merged file should look something like this:

{ "values": [ "load:load", "your_pack:load" ]}

This library uses Lantern Load.

How it works

This library uses the /attribute [...] get command to read the players equipment instead of other checks. Running two attribute commands each tick is a lot more efficient compared to other methods, where you read nbt or check components for multiple items each tick.

Equipment is identified using the luck attribute in very low amounts since the luck attribute is only used in the fishing loot table and only influences the loot table at integer values (1, 2, 3, ...). Attributes in minecraft are stored as doubles and when reading them for use in the loot table, everything after the decimal point just gets cut (4.69 becomes 4), so values little over 0 are effectively read as 0.

This library uses specific uuids of the generic.luck attribute modifier to identify the different tungsten slots. When creating an item, the amount of the attribute modifier gets set to -9.094947017729282e-13 (-2-40) to initialize the library and give each item a unique id. These uids get stored back into the attribute amount as to not repeat the setup.

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Copyright © 2023 Smithed
Not an official Minecraft product. Not approved by or associated with Mojang Studios