Not sure what you mean by "IT tool". Maybe "IT tool" has a special meaning?
Otherwise, EAD is XML. Any xml editor (e.g. oxygen) or parser (e.g. saxon) can validate it, as well as many web browsers (though their error reporting isn't always very helpful).
From: Encoded Archival Description List [mailto:[log in to unmask]] On Behalf Of Arian Rajh
Sent: Tuesday, September 27, 2016 6:38 AM
To: [log in to unmask]
Subject: EAD3 validator
Is there a validator/validation IT tool for checking technical validity of archival description formatted as EAD xml file (and according to EAD3 tags).