All available options will be listed here. These options must be placed under the Options: tag inside your item configurations.

example_item:
  Id: diamond
  Options:
    SomeOption: value

Universal Options

These options are applicable to all items:

Repairable

Sets the repair cost of the item to maximum, making it completely uneditable in anvils and/or enchantment tables.
Will override the RepairCost option.
Defaults to false.

  Options:
    Repairable: false

RepairCost

Sets the repair cost of the item.
If set to less than 0, the vanilla one will be used.
Defaults to -1.

  # Not an option, apparently, but kept here because of repairable
  RepairCost: 10

Unbreakable

Sets the unbreakable tag on the item.
Items with this set to true will not lose durability.
Defaults to false.

  Options:
    Unbreakable: true

Glint

Adds the enchantment glint visual effect to an item Defaults to false.

  Options:
    Glint: true

HideFlags

Note: this feature does not exist >=1.20.5! Use this instead

Hides all the item flags, making things like enchants not visible in the item's lore (please note however that the item will still have an enchanted glow).
Defaults to false.

  Options:
    HideFlags: true

PreventStacking

Prevents the item from stacking to similar items.
Defaults to false.

  Options:
    PreventStacking: true

StackSize

Sets the maximum stack size of the item in the inventory. Does not work when used alongside attributes.

  Options:
    StackSize: 16

GenerateUUID

Applies a random UUID to the item upon generation. Useful to easily detect duped items. Enabling this option automatically prevents similar items from stacking, as they share different UUIDs.

  Options:
    GenerateUUID: true

GenerateTimestamp

Applies the current unix time to the item on generation. Useful to backtrack the exact time an item was created. Enabling this option will prevent items from stacking if they were generated at different times.

  Options:
    GenerateTimestamp: true

ItemModel

The model that should be applied to the item, which works like this item component

MODELED_ITEM:
  Id: PAPER
  Display: '&dKing Helmet'
  Options:
    ItemModel: SomeModel

FireResistant

Whether the item is resistant to fire, as netherite is.
Defaults to false.

  Options:
    FireResistant: true

Playerheads

Only applicable to playerhead type items

Player

Sets the texture of the player head.
The value must be the IGN of the target player.
Player heads must use data value 3 for this to work.

  Options:
    Player: Herobrine

SkinTexture

Also sets the texture of the player head, but instead uses a SkinURL.

• Type into browser: https://sessionserver.mojang.com/session/minecraft/profile/trimmeduuidofplayerhere.
• Use http://mcuuid.net/ to find the trimmed uuid of the player.

Player heads must use data value 3 for this to work.
This option also supports hashes.

  Options:
    SkinTexture: eyJ0ZXh0dXJlcyI6eyJTS0lOIjp7InVybCI6Imh0dHA6Ly90ZXh0dXJlcy5taW5lY3JhZnQubmV0L3RleHR1cmUvODdlMGFhOTQzM2RiYTliNzU5MzJhMTFkYzk0ZDQwNmJkZTE5ZTg2MzUxNDIxNDkyYjNlZDM3OGM4ZTFhN2NjIn19fQ==

Dyeable Items

Color

Dyes the armor piece to a color according to RGB settings. 0-255.
Alternately can use a predefined color. Found here.
Can pick colors using the Paint program on Windows. Open it up then choose "Edit Colors" to get your RGB value.
Only usable on leather armor type, banners, shields and such.

  Options:
    Color: RED

  Options:
    Color: 102,102,153

Examples

ClothSlippers:
  Id: 301
  Data: 0
  Display: '&fCloth Slippers'
  Lore:
  - ''
  - 'So Soft!'
  - ''
  Enchantments:
  - DURABILITY:1
  Options:
    Color: 200,200,200

Lots of possible options included:

TestHead:
  Id: 397
  Data: 3
  Options:
    Player: Rickyling

dat_item_though:
  Id: banner
  Data: 4
  Display: '&c&lThe Banner&r'
  Lore:
  - ''
  - '&rIt<&sq>s the perfect stone.'
  - '&cNever question that.'
  - ''
  Amount: 8
  Options:
    Color: 200,200,200
    Unbreakable: true
  Enchantments:
  - DURABILITY:1
  - ARROW_FIRE:10

An example of a firework rocket

FireworkGoBoom:
  Id: FIREWORK_ROCKET
  Display: 'Rocket'
  Firework:
    Colors:
    - 255,0,255
    - 0,0,0
    FadeColors:
    - 200,0,0
    Flicker: true
    Trail: true