Embodiments of the invention provide a guided surgical tool assembly with a guide tube including a sensor, a surgical instrument including a detectable feature moveable within the guide tube, and the sensor capable of detecting the detectable feature when the surgical instrument is inserted in the guide tube. Some embodiments include a sensor pad, a guide stop coupled to the surgical instrument, a plunger mechanism including a compressible spring mechanism coupled to the guide tube, and a wiper capable of being sensed by the sensor pad. Some embodiments include a guided surgical tool assembly system comprising a tool sensor system including a processor and at least one data input/output interface. Some embodiments include a medical robot system with a guided surgical tool assembly and including a robot coupled to an effectuator element configured for controlled movement and positioning along one or more of an x-axis, a y-axis, and a z-axis.