A minimally invasive surgical tool comprising: a tubular instrument shaft having a proximal end, a distal end, and a bore between the proximal end and the distal end, the shaft having an instrument shaft axis defined between the proximal end and the distal end; an end effector comprising an end effector body; an intermediate wrist member pivotally coupled with the distal end of the shaft and pivotally coupled with the end effector body, wherein pivoting of the intermediate member relative to the shaft orients the intermediate member about a first axis relative to the shaft, and wherein pivoting of the end effector body relative to the intermediate member orients the end effector about a second axis relative to the intermediate member, the first axis being transverse to the shaft axis, the second axis being transverse to the first axis, the intermediate member having an exterior width along the first axis and an exterior length along the second axis, the length being significantly greater than the width so that the intermediate member has an elongate cross section; and an actuation system including a plurality of tension members (188, 190, 192, 194) extending distally through the bore of the shaft and interfacing with the end effector, the actuation system orienting the end effector body and actuating the end effector, each of the tension members (188, 190, 192, 194) being laterally separated from the intermediate member and the first and second axes between the shaft and the end effector body, characterized in that the actuation mechanism further includes a first rotatable drive shaft for driving a first actuation mechanism of the end effector, the first drive shaft being routed between the end effector body and the bore so as to pass adjacent to a first side of the intermediate member and the rotation axis of the first rotatable drive shaft being parallel to the instrument shaft axis. a tubular instrument shaft having a proximal end, a distal end, and a bore between the proximal end and the distal end, the shaft having an instrument shaft axis defined between the proximal end and the distal end; an end effector comprising an end effector body; an intermediate wrist member pivotally coupled with the distal end of the shaft and pivotally coupled with the end effector body, wherein pivoting of the intermediate member relative to the shaft orients the intermediate member about a first axis relative to the shaft, and wherein pivoting of the end effector body relative to the intermediate member orients the end effector about a second axis relative to the intermediate member, the first axis being transverse to the shaft axis, the second axis being transverse to the first axis, the intermediate member having an exterior width along the first axis and an exterior length along the second axis, the length being significantly greater than the width so that the intermediate member has an elongate cross section; and an actuation system including a plurality of tension members (188, 190, 192, 194) extending distally through the bore of the shaft and interfacing with the end effector, the actuation system orienting the end effector body and actuating the end effector, each of the tension members (188, 190, 192, 194) being laterally separated from the intermediate member and the first and second axes between the shaft and the end effector body,