As to something
Definition 1 of 2
Pro Tip 1/3Expression of Doubt
Use 'as to' to express uncertainty or doubt about a subject. 
There's some hesitation as to whether to accept the job offer.
Pro Tip 2/3Decision Clarification
'As to' can clarify the specific aspect of a decision being discussed. 
We need a decision as to the venue for the event.
Pro Tip 3/3Detail Introduction
Introduce details or specifics on a topic using 'as to'. 
He gave a thorough explanation as to why the project failed.