# How does Dragon Hide interact with monk AC? [duplicate]

Before I begin let me preface this with the following: I understand that mechanically speaking the barbarian and Monk armor classes are calculated 10 + Dex mod + Wis/Con depending on the class played. My conundrum is this: One of my players is playing a Dragon Born Monk who just got to level 4, He has decided on taking the racial feat Dragon Hide. The feat reads as:

You manifest scales and claws reminiscent of your draconic ancestors. You gain the following benefits:

Your scales harden. While you aren't wearing armor, you can calculate your AC as 13 + your Dexterity modifier. You can use a shield and still gain this benefit.

Now the question: As monk uses Wisdom and Dexterity to calculate AC and as they don't wear armor or use shields anyway, is this just adding a +3 Natural Armor bonus to his base AC?

I have seen some debate go back and forth saying that this would be legal while others are claiming that by taking the feat he is actually changing how his AC is calculated. Rather than the feat adding Natural Armor to his base AC. So the second part of the question is: If this is something doesn't work Would this be game breaking in someway? As it stands right now from my perspective I would have to say I am leaning slightly on the side of allowing it due to the nature of how he got the bonus.

First he had to take the feat at 4th instead of an attribute increase, Second it does not clash with the concept of the monk who uses insight and agility to deflect/dodge incoming attacks, adding scales doesn't make one less insightful or less dexterous. But I am posting this because I am still on the fence. Please and than you for your insights.