Developing vision-based 3D gestures recognition systems requires strong expertise and knowledge in computer vision and machine learning techniques. As human-computer interaction researchers do not generally have a thorough knowledge of these techniques, we developed Gesta. Gesta is a tool that enables non-experts in vision computing and artificial intelligence techniques to rapidly develop a 3D gestures recognition system prototype and to support the gesture design process. This tool works with up to two Microsoft Kinects, and integrates the depth cameras calibration algorithm and the hidden Markov models classifier. The users can manage these complex functions through a simple graphical user interface, even if they do not have any expertise in computer vision and machine learning domains. A usability test with 12 researchers with experience in human-computer interaction has been conducted in order to evaluate the overall usability of this tool. Results demonstrate that the testers appreciated the Gesta tool which scored 88.9 points out of 100 in the Brooke's system usability scale.