The entry for Mason’s Tools within the PHB (p154) lists this as one of the proficiency’s benefits:
Demolition. Your knowledge of masonry allows you to spot weak points in brick walls. You deal double damage to such structures with your weapon attacks.
It then lists this as one of the possible activities:
Find a weak point in a stone wall [DC 15]
One might interpret this to mean that you must make a successful DC15 check with the Mason’s Tools before being able to deal double damage to a stone structure with your weapon attacks.
Another might read these as isolated entries, believing that your proficiency with Mason’s Tools automatically allows you deal double damage to stone structures with your weapon attacks as a passive benefit. Meanwhile, successfully performing the tool check above bestows its own separate benefit.
Obviously, the confusion lies in their using the phrase "weak point" in both the Activity as well as the Demolition feature. However, if read literally, the Demolition feature does explicitly state "You deal double damage to such structures…" and not "you deal double damage to weak points within such structures…".
So, to word this as questions:
Do you need to perform to a successful tool check to benefit from the Demolition feature of the Mason’s Tools?
And if not, what would be the benefit of finding a weak point in a stone wall with a successful check of the Mason’s Tools? (For example: Would a weak point within a stone structure simply have fewer hit points than the rest of that structure?)