This paper presents an overview of the use of robots in medicine and specifically in neurosurgery. The RONNA system, which has been developed at the Faculty of Mechanical Engineering and Naval Architecture in collaboration with the University Hospital Dubrava in Zagreb, is presented, for which the concept of a robotic tool for brain tumor biopsy is being developed. After analyzing the functionality of the desired robotic tool, an iterative development of an individual parts is shown through the paper, which, individually or in combination, helps to fulfill certain functions. Given design solutions of specific problems, which must be fulfilled in order to maintain their functions, have been developed sequentially, with the valid interrelationship of parts. Each design solution is presented through phases that have been upgraded through four cycles to satisfy all functionalities. Finally, variants of the concept of a robotic tool are presented through the same cycles in which elements of the entire system were developed. The last variant shown is the result of design development and the solutions obtained, along with standard and existing industry elements, fulfill all the functionalities of a robotic brain tumor biopsy tool. In addition to the fully functional design, a critical review with tolerance analysis is presented.