In the past few years, several robotic end-effectors based on diverse kinematics and actuation principles have been developed to provide grasping and manipulation functionalities. To ease the control and application of these wide-ranging end-effectors, the development of effective reusable tools that can facilitate the end-effector motion planning and control is necessary. In this work, we introduce a generic grasp planner that leverages on the concept of the primitive grasping actions. Given the specific characteristics of an end-effector, including its kinematic and actuation arrangements, a number of primitive grasping actions are extracted and employed by the proposed grasp planner to autonomously plan and synthesize more complex grasping behaviours. The grasp planner is validated through experimental trials involving the HERI II robotic hand, a four-fingers tendon-driven under-actuated hand. The results of these experiments demonstrate the efficacy of the proposed method to generate appropriate planning actions enabling to grasp objects of different shapes.