The implementation of IoT (Internet of Things) systems is difficult since the data sent from the devices is complex, especially in agriculture and agroecology, where it is generated from heterogeneous hardware and software, and its applications involve different actors. In this scenario, conceptual design is mandatory to provide a formal and unambiguous representation allowing the different actors to set their requirements. The problem with the current representations is that they do not take into account neither the internal parameters nor the dynamic aspect of smart devices. To fill this gap we propose SmartSTS4IoT, an extension of the STS4IoT UML profile that models the different representations of internal/external data expressed from the same sensor and the logic used to adapt the sending/sensing policies to sudden environmental changes. The profile is illustrated with reference to a case study in the context of smart agriculture and validated theoretically.