So, likely descriptive but may be either depending on how the deed is drafted, and depending on whether it's in an exhibit that is incorporated by reference into the deed or not. However, what likely governs is not the description/prescription in any event; it is whether your deed allows for an easement and the board has approved it.
Most master deeds for condominiums have what is called an "Easement of Encroachment" in the body of deed (usually shortly after the name, description of land, description of building, description of unit(s)), so that each unit has the benefit of an easement of encroachment in the event that said unit (meaning any unit) encroaches upon any portion of the common elements of the structure or another unit (encroachment on another unit is only for things like building settling that causes the building lines to move or change slightly – you can't bump out your closet a foot into your neighbor's room). This easement goes both ways, or vice versa, such that common elements may encroach upon the unit for a variety of different reasons like building maintenance and building settling; i.e., the whole has the same rights.
The part that is really relevant in your case, however, and is very typical language, is the part that typically states something like: each unit has and is subject to an easement for the benefit of any other unit, to use and access such elements to encompass wires, ducts, pipes, conduits, cables or any other common elements located in, on, or within the right of any unit such that if improvements to a unit that are within your right under the restrictive covenants (the vote would decide that in your case) then those common elements may be changed to the extent that they do not materially and adversely affect another unit. This does not mean that another unit does not like it. It means that it would materially change their unit in some way, like the shape of it, the water available to them, etc. You should check the master deed for this. Otherwise, the covenants control and you still should have the right to do this. You may potentially just need to amend the description of your unit. Even if an amendment needs to get filed with the registry of deeds, that is not a big deal. I hope this helps.