A rotary steerable tool shut-off system comprising: a fluid control valve body having an inner chamber with cylindrical side walls, a piston gallery extending between the inner chamber and a piston port , and an exhaust gallery extending between the inner chamber and an exhaust port , the inner chamber having a drilling fluid inlet port ; a spool in the inner chamber, the spool having a spool shaft extending longitudinally along a central axis of the inner chamber from a transverse flange , a first passage that extends longitudinally through at least a portion of the spool shaft, and at least one spool inlet port providing fluid communication between an outer surface of the spool shaft and the first passage, wherein the first passage can be in fluid communication with the drilling fluid inlet port but not the exhaust port, and a second passage in the spool that can be in fluid communication with the exhaust port but not the drilling fluid inlet port; a piston shut off valve rotatably mounted on the spool shaft, wherein the piston shut off valve includes a shut off valve port which provides fluid communication between the inner chamber and the outer surface of the spool shaft; wherein the piston shut off valve can rotate to a first position relative to the spool shaft such that the shut off valve port at least partially overlaps with the spool inlet port to provide fluid communication between the first passage and the drilling fluid inlet port, and wherein the piston shut off valve can rotate to a second position relative to the spool shaft such that the shut off valve port does not overlap with the spool inlet port and seals the first passage from fluid communication with the drilling fluid inlet port. a fluid control valve body having an inner chamber with cylindrical side walls, a piston gallery extending between the inner chamber and a piston port , and an exhaust gallery extending between the inner chamber and an exhaust port , the inner chamber having a drilling fluid inlet port ; a spool in the inner chamber, the spool having a spool shaft extending longitudinally along a central axis of the inner chamber from a transverse flange , a first passage that extends longitudinally through at least a portion of the spool shaft, and at least one spool inlet port providing fluid communication between an outer surface of the spool shaft and the first passage, wherein the first passage can be in fluid communication with the drilling fluid inlet port but not the exhaust port, and a second passage in the spool that can be in fluid communication with the exhaust port but not the drilling fluid inlet port; a piston shut off valve rotatably mounted on the spool shaft, wherein the piston shut off valve includes a shut off valve port which provides fluid communication between the inner chamber and the outer surface of the spool shaft; wherein the piston shut off valve can rotate to a first position relative to the spool shaft such that the shut off valve port at least partially overlaps with the spool inlet port to provide fluid communication between the first passage and the drilling fluid inlet port, and wherein the piston shut off valve can rotate to a second position relative to the spool shaft such that the shut off valve port does not overlap with the spool inlet port and seals the first passage from fluid communication with the drilling fluid inlet port. <EOS>