Smart antennas are an enabling technology for the new generation of communication and sensing systems [1]. Reconfigurable metasurfaces have been envisioned as one of the main components for future high-capacity smart radio environments. The development of cost-effective reconfigurable solutions capable of operating at high frequencies (such as sub THz and THz) is one of the main bottlenecks for this technology. One key challenge is to model properly the intrinsic complexity of this type of antenna [2]. The numerical solution of Maxwell's equations through full wave methods provides the most accurate description of the reconfigurable metasurface. It is necessary to model properly the unit cells that comprise the metasurface accounting for the embedded switching devices. Typically, these switches are characterized using equivalent circuit models that can be validated from direct probing measurements made on test fixtures (Figure 1). The design of electrically large apertures, composed by hundreds of thousands of elements, is particularly time-consuming. The associated high computational resources limit the generalized use of the previously mentioned tools. This kind of simulation is only feasible in a confined spatial region next to the antenna aperture. The physical source may only be included in the model when located within the near-field region of the metasurface. In this case, the primary source and the metasurface are considered as an antenna, described by its gain. Alternatively, the metasurface can be placed in the far-field region of the source implying that, from the aperture perspective, the incoming signal is a plane wave. In this case, the metasurface is characterized by its RCS and the link budget is calculated using the usual bi-static radar formula. In this work, we present the design process of reconfigurable metasurfaces assisted by full wave methods, showing some experimental examples developed within the context of the on-going EU project – TERRAMETA [3].