This paper presents a method and the associated authoring tool for supporting the development of interactive applications able to access multiple Web Services, even from different types of interactive devices. We show how model-based descriptions are useful for this purpose and describe the associated automatic support along with the underlying rules. The proposed environment is able to aid in the design of new interactive applications that access pre-existing Web Services, which may contain annotations supporting the user interface development. This is achieved through the use of task models as a starting point for the design and development of the corresponding implementations. We also provide an example to better illustrate the features of the approach, and report on two evaluations conducted to assess the support tool.