The problem with an agent taking responsibility for this type of information is that it can change. If on Tuesday they tell you, and thus take responsibility for the accuracy for the information that there are no registered sex offenders in the neighborhood and on Wednesday one arrives, the agent didn't do anything wrong but you are still going to be ticked off. This information is generally available through state or county websites like the one I've posted below and I encourage my clients to do their own research by checking such sites and actually meeting neighbors prior to being fully contractually committed.
One other consideration, these sites can only tell you where the "registered" sex offenders are supposed to be. Often times, the unregistered and mobile ones are just as big of a risk. There is also the risk one moves in next door the day after closing. There is only so much you can do.