Nystul's Magic Aura (PHB p.263) lets you
[…] change the way the target appears to spells and magical effects, such as detect magic, that detect magical auras. You can make a nonmagical object appear magical […]
And with Identify (PHB p.252) you can (emphasis mine)
[…] choose one object that you must touch throughout the casting of the spell. If it is a magic item or some other magic-imbued object, you learn its properties and how to use them, whether it requires attunement to use, and how many charges it has, if any. You learn whether any spells are affecting the item and what they are. If the item was created by a spell, you learn which spell created it.
My question is, whether Identify counts as spell "that detect[s] magical auras". If it does what would it show to the caster when it is affected by Nystul's Magic Aura. Can the caster of Nystul's Magic Aura choose the effect Identify shows?
Also, what are other spells or effects than detect magic that "detect magical auras". Do they have to explicitly mention that they work by detecting magical auras?
Best Answer
Interpreting the language of descriptions is left to the DM. To me it is clear that the intention was to hinder any divination spell that reveals information about magical properties, but this is my interpretation, so check with your DM.
Due to the magic aura, identify will show obfuscated or false information, but it will also detect that the item is under the magic aura spell. While you know that the information might be falsified, you cannot identify its true properties until you get rid of the aura (with dispel magic or letting its duration end).
The spell explicitly states that you can change whether the item appeares magical or not. Beyond that you can make it show that the magic belongs to a specific school of magic. This is mainly designed to fool detect magic. Because identify reveals the magic aura spell anyway, showing a specific ability or effect would be pointless.