For this type of quest you must specify an item, with the line :
required_item:<TYPE>
It is not mandatory to specify an item. Simply remove this line from your quest to take into account all items involved in the quest type. For example, a BREAK quest will include all broken blocks if none are specified.
All types of items are listed on this page.
Custom items
For quests that require an item, you can specify a custom item.
You must then specify in required_itemthe type CUSTOM_ITEM.
Then, below, you must specify the name of the item and its description.
For quests that require a potion, you can specify the type and whether it should be upgraded or expanded. To do this, you can add a potion section to your quest setup, like this: