A good long-form item description should first explain what the item is, then:

• Explain what the item can be used for (if non-obvious)
• If the item can be sold for a large amount of money or is not usable, explain why an NPC would want to buy it
• Explain what (if anything) drops the item and why (optional, and if non-obvious)
• Provide lore related to the mob that drops it
• Provide lore related to NPCs or players who might have used the object.