Sometimes normal items won't cut it:

Sometimes we want to be able to specify recipes that only work when the input item fulfills some conditions.

Sometimes we want to be able to specify recipes that will produce a special item, be it with NBT-Tag or Damage value or otherwise.

It might be required for you to import the package if you encounter any issues (like casting an Array), so better be safe than sorry and add the import.
import crafttweaker.item.IItemCondition;

These will affect the items that you can use to craft the resulting item. Remember, you can mix modifiers, to mix Damage and NBT-Tag, for example

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<minecraft:iron_pickaxe>.onlyDamaged().withTag({display: {Lore: "Aren't we all butterflies?"}});

The input item's damage value does not matter for the recipe

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item.anyDamage()

The input item needs to be damaged

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item.onlyDamaged();

Input item's damage value needs to be at least the specified value
Value is an int

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item.onlyDamageAtLeast(value);

Input item's damage value needs to be at max the specified value
Value is an int

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item.onlyDamageAtMost(value);

Input item's damage value needs to be between the speciefied value1 and value2
Value1 is an int
Value2 is an int

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item.onlyDamageBetween(value1, value2);

Sometimes you need a recipe where you get some of your input items back.
By applying transformDamage(int) you can create such recipes.

The input item will receive value damage points and you will get it back, unless it breaks during the crafting process.
Value is an int

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item.transformDamage(value);

Sometimes you want your ingredients to need a specific NBT-Tag. The recipe doesn't care if your item has NBT-Tags other than the ones specified, So a pickaxe with a specific lore may also be enchanted!

If you use withTag jei will display it properly, if you use onlyWithTag, jei will only display a tagless item!

Here's how you do it: NBTTag is your NBT Data

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item.withTag(NBTData);
item.onlyWithTag(NBTTag);

<minecraft.iron_pickaxe>.onlyWithTag({display: {Name: "Pickle the Pickleberry"}});
<minecraft.iron_pickaxe>.withTag({display: {Name: "Pickle the Pickleberry"}});

If you can specify input conditions, it's not so hard to also define output conditions, or rather, output modifiers.

Your output item will have value damage points.
Value is an int.

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item.withDamage(value);

Your output item will have NBTTag as NBT-Tag.
NBTTag is your NBT Data

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item.withTag(NBTTag);

<minecraft:iron_pickaxe>.withTag({display: {Name: "Pickle the Pickleberry"}})

You can also add your own itemConditions. These are special functions that accept the item itself as single parameter.

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conditionedItem = item.only(function(item) {return true;});

The function needs to return a bool that is true if the item matches the condition.