A context-descriptive prototype is an interactive graphical animation, driven by a formal, executable engine, implemented in some programming or modelling language. The two main properties of a context-descriptive prototype are: (1) it is an integrated description that describes system, work processes, and context of use; (2) it is a formal description. Because of (1), designers, including users, are provided with a means to investigate the system in the context of the envisioned work processes. Because of (2), investigations into questions of formalisation and automation, not only of the system, but also of the work processes, can be made explicitly and become subject for discussions and further elaboration. We describe a concrete context-descriptive prototype of the hospital work process medicine administration and its support by a new pervasive system. We discuss findings from evaluation of the prototype in cooperation with nurses, and finally compare context-descriptive prototypes with other kinds of prototypes.