Congressional monitoring by committees of the activities of executive branch agencies, to determine if the laws are being faithfully executed, is called

It is called congressional oversight.

Congressional oversight is the power to investigate and oversee the executive branch and it is usually carried out by the congressional committees.

Congressional oversight includes monitoring and supervising of federal agencies, programs, activities and policy implementation. In some cases, an investigation into an irregularity, a political scandal or into executive branch operations may be necessary.

This oversight authority derives from the implied powers in the Constitution and it is an integral part of the American system of checks and balances.