When directed by the court, the probation agent must fully investigate and report to the court in writing the circumstances of the offense and the criminal record, social history, and present condition of the defendant including, whenever practicable, the findings of a physical and mental examination of the defendant. When the services of a probation agent are available to the court, no defendant charged with a felony and, unless the court shall direct otherwise in individual cases, no other defendant may be placed on probation or released under suspension of sentence until the report of such investigation has been presented to and considered by the court.