Implantable applications have been increasing in number in an exponential manner since the turn of the millennium. This is largely due to the increasing availability of ultra low power consumption electronics, enabling the emergence of healthcare services using implantable or swallowable sensors. Other fields of applications exist, e.g. in the domains of military, security or sports. A large number of antennas for these implantable or swallowable capsules have been designed, and can be found in the literature. They are however always presented for a specific capsule and application, and are thus very difficult to compare in terms of antenna characteristics. In this paper, we show results obtained for simple canonical implantable radiation sources, obtained using a specifically developed numerical tool presented earlier. These canonical results will allow us to obtain some simple but useful figures of merit that enable an easy assessment of the quality of the radiation characteristic of a specific antenna design in a specific capsule