mcf-item-modifier

name	mcf-item-modifier
description	Create and modify Minecraft Java Edition item modifier definitions. Use when working with item modification functions in loot tables or via /item modify command. Covers all 40+ modifier types with complete field reference for version 26.1.2.
license	MIT
compatibility	opencode
metadata	{"version":"1.0","game-version":"26.1.2","category":"minecraft-datapack"}

Minecraft Item Modifiers

File Location

data/<namespace>/item_modifier/<path>.json

Usage

item modify entity @s weapon.mainhand namespace:modifier_name
item replace block ~ ~ ~ container.0 from entity @s weapon.mainhand namespace:modifier_name

Basic Format

Single modifier:

{
  "function": "minecraft:set_count",
  "count": 1
}

Multiple modifiers (array):

[
  { "function": "minecraft:set_count", "count": 1 },
  { "function": "minecraft:set_name", "name": "My Item" }
]

With conditions:

{
  "conditions": [
    { "condition": "minecraft:random_chance", "chance": 0.5 }
  ],
  "function": "minecraft:set_count",
  "count": 64
}

Modifier Types Reference

Count & Quantity

set_count - Set or modify item count:

{
  "function": "minecraft:set_count",
  "count": { "type": "minecraft:uniform", "min": 1, "max": 3 },
  "add": false
}

limit_count - Clamp item count:

{
  "function": "minecraft:limit_count",
  "limit": { "min": 1, "max": 64 }
}

enchanted_count_increase - Enchantment-based count:

{
  "function": "minecraft:enchanted_count_increase",
  "enchantment": "minecraft:fortune",
  "count": 1,
  "limit": 64
}

Enchantment

enchant_randomly - Random enchantment:

{
  "function": "minecraft:enchant_randomly",
  "only_compatible": true,
  "options": ["minecraft:sharpness", "minecraft:smite"]
}

Options can be a tag: "#minecraft:on_random_loot"

enchant_with_levels - Enchant at specific level:

{
  "function": "minecraft:enchant_with_levels",
  "levels": { "type": "minecraft:uniform", "min": 5, "max": 30 },
  "options": "#minecraft:on_random_loot"
}

set_enchantments - Set specific enchantments:

{
  "function": "minecraft:set_enchantments",
  "enchantments": {
    "minecraft:sharpness": 5,
    "minecraft:unbreaking": 3
  },
  "add": false
}

Item Name & Lore

set_name - Set custom name (text component):

{
  "function": "minecraft:set_name",
  "name": { "text": "Sword of Destiny", "color": "gold", "italic": false },
  "entity": "this"
}

set_lore - Set lore lines:

{
  "function": "minecraft:set_lore",
  "lore": [
    { "text": "A legendary weapon", "color": "gray" }
  ],
  "mode": "replace_all"
}

Modes: replace_all, append, insert, replace_section

copy_name - Copy entity name to item:

{
  "function": "minecraft:copy_name",
  "source": "block_entity"
}

Sources: this, attacker, last_damage_player, block_entity, direct_attacker

Components & Data

set_components - Set item stack components:

{
  "function": "minecraft:set_components",
  "components": {
    "minecraft:custom_name": "{\"text\":\"Custom\"}",
    "minecraft:enchantment_glint_override": true,
    "!minecraft:unbreakable": {}
  }
}

Use !component_name to remove a component.

copy_components - Copy components from source:

{
  "function": "minecraft:copy_components",
  "source": "block_entity",
  "include": ["minecraft:custom_name"],
  "exclude": []
}

set_custom_data - Set custom_data component:

{
  "function": "minecraft:set_custom_data",
  "tag": "{my_key: 123, my_string: \"hello\"}"
}

String or object format. Merges into existing custom_data.

copy_custom_data - Copy NBT to custom_data:

{
  "function": "minecraft:copy_custom_data",
  "source": { "type": "context", "target": "block_entity" },
  "ops": [
    { "op": "replace", "source": "Items", "target": "stored_items" }
  ]
}

Ops: replace, append, merge. Source: context or storage.

Damage & Durability

set_damage - Set durability ratio:

{
  "function": "minecraft:set_damage",
  "damage": 0.5,
  "add": false
}

damage is a ratio (0.0-1.0). add=true makes it additive.

Contents & Container

set_contents - Set container-like contents:

{
  "function": "minecraft:set_contents",
  "component": "container",
  "entries": []
}

Component types: container, bundle_contents, charged_projectiles

modify_contents - Modify item contents:

{
  "function": "minecraft:modify_contents",
  "component": "container",
  "modifier": { "function": "minecraft:set_count", "count": 1 }
}

Books

set_book_cover - Set written book metadata:

{
  "function": "minecraft:set_book_cover",
  "title": { "raw": "My Story", "filtered": "My Story" },
  "author": "PlayerName",
  "generation": 1
}

set_writable_book_pages - Set book & quill pages:

{
  "function": "minecraft:set_writable_book_pages",
  "pages": ["Page 1", "Page 2"],
  "mode": "replace_all"
}

set_written_book_pages - Set signed book pages:

{
  "function": "minecraft:set_written_book_pages",
  "pages": [{ "raw": "Content", "filtered": "Content" }],
  "mode": "replace_all"
}

Fireworks

set_fireworks - Set firework rocket data:

{
  "function": "minecraft:set_fireworks",
  "flight_duration": 3,
  "explosions": {
    "values": [{
      "shape": "large_ball",
      "colors": [16711680, 65280],
      "fade_colors": [255],
      "trail": true,
      "twinkle": false
    }],
    "mode": "replace_all"
  }
}

set_firework_explosion - Set firework star data (same fields as above, single explosion).

Special Items

set_potion - Set potion type:

{ "function": "minecraft:set_potion", "id": "minecraft:long_swiftness" }

set_random_potion - Random potion from options:

{
  "function": "minecraft:set_random_potion",
  "options": [
    { "type": "minecraft:uniform", "min": 0, "max": 5 }
  ]
}

set_ominous_bottle_amplifier - Set ominous bottle level:

{
  "function": "minecraft:set_ominous_bottle_amplifier",
  "amplifier": { "type": "minecraft:uniform", "min": 0, "max": 4 }
}

set_stew_effect - Set suspicious stew effects:

{
  "function": "minecraft:set_stew_effect",
  "effects": [
    { "type": "minecraft:night_vision", "duration": 100 }
  ]
}

set_instrument - Set goat horn instrument:

{ "function": "minecraft:set_instrument", "options": "#minecraft:goat_horns" }

set_random_dyes - Set random dye on dyeable item:

{
  "function": "minecraft:set_random_dyes",
  "from_options": false
}

exploration_map - Convert to explorer map:

{
  "function": "minecraft:exploration_map",
  "destination": "on_treasure_maps",
  "decoration": "target_point",
  "zoom": 2,
  "search_radius": 50,
  "skip_existing_chunks": true
}

fill_player_head - Set player head owner:

{
  "function": "minecraft:fill_player_head",
  "entity": "this"
}

Attributes & Banners

set_attributes - Set attribute modifiers:

{
  "function": "minecraft:set_attributes",
  "modifiers": [{
    "attribute": "minecraft:generic.attack_damage",
    "operation": "add_value",
    "amount": 5,
    "id": "namespace:custom_bonus",
    "slot": "mainhand"
  }],
  "replace": true
}

Operations: add_value (Op0), add_multiplied_base (Op1), add_multiplied_total (Op2)

set_banner_pattern - Set banner patterns:

{
  "function": "minecraft:set_banner_pattern",
  "patterns": [
    { "pattern": "minecraft:stripe_top", "color": "red" },
    { "pattern": "minecraft:stripe_bottom", "color": "blue" }
  ],
  "append": false
}

Custom Model Data

set_custom_model_data - Set model override data:

{
  "function": "minecraft:set_custom_model_data",
  "floats": { "values": [1.0, 2.5], "mode": "replace_all" },
  "flags": { "values": [true, false], "mode": "replace_all" },
  "strings": { "values": ["variant_a"], "mode": "append" },
  "colors": { "values": [16711680], "mode": "replace_all" }
}

Modes: replace_all, replace_section, append, insert

Utility

apply_bonus - Enchantment-based bonus count:

{
  "function": "minecraft:apply_bonus",
  "enchantment": "minecraft:fortune",
  "formula": "uniform_bonus_count",
  "parameters": { "bonusMultiplier": 1 }
}

Formulas: uniform_bonus_count, ore_drops, binomial_with_bonus_count

copy_state - Copy block state to item:

{
  "function": "minecraft:copy_state",
  "block": "minecraft:oak_log",
  "properties": ["axis"]
}

set_item - Replace with different item:

{
  "function": "minecraft:set_item",
  "item": "minecraft:stone"
}

set_loot_table - Set loot table on container item:

{
  "function": "minecraft:set_loot_table",
  "name": "minecraft:chests/simple_dungeon",
  "seed": 12345
}

furnace_smelt - Convert to smelting result:

{ "function": "minecraft:furnace_smelt" }

explosion_decay - Apply explosion decay (1/radius chance to vanish):

{ "function": "minecraft:explosion_decay" }

discard - Remove the item stack:

{ "function": "minecraft:discard" }

toggle_tooltips - Toggle tooltip visibility:

{
  "function": "minecraft:toggle_tooltips",
  "toggles": {
    "minecraft:enchantments": false,
    "minecraft:stored_enchantments": true
  }
}

Flow Control

filtered - Conditional modifier application:

{
  "function": "minecraft:filtered",
  "item_filter": { "items": ["minecraft:diamond"] },
  "on_pass": { "function": "minecraft:set_count", "count": 64 },
  "on_fail": { "function": "minecraft:discard" }
}

sequence - Apply modifiers sequentially:

{
  "function": "minecraft:sequence",
  "functions": [
    { "function": "minecraft:set_count", "count": 3 },
    { "function": "minecraft:enchant_randomly" }
  ]
}

reference - Reference another modifier file:

{ "function": "minecraft:reference", "name": "namespace:other_modifier" }