Disclosed herein is a lead insertion tool for inserting a lead connector end of an implantable lead into a lead receptacle of a header of an implantable pulse generator, the implantable lead including a lead body extending distally from the lead connector end. The tool includes a lead pathway and an engagement mechanism. The lead pathway extends through the tool and is configured to receive the implantable lead. The engagement mechanism includes an engaged state and a self-biasing non-engaged state. When the engagement mechanism is self-biased into the non-engaged state, the implantable lead is free to displace along the lead pathway. When the engagement mechanism is forced into the engaged state, the lead cannot displace along the lead pathway.