This article discusses the use of artifacts as an instrument-mediated activity based on a field study in a call center specialized in networks and telecommunications. In this work setting, operators have access to a knowledge-sharing database, which is designed to support the collective elaboration of individual knowledge diffused on hot-lines in an instrument as a means for the collective activity. We characterize this situation along two interrelated analytical dimensions: the design-in-use process by analyzing operators' activities: hot-line assistance and knowledge base appropriation; the design-for-use process by analyzing the design assumptions inscribed in the artifact developed by designers. Main results showed that the experts' dialogue-conducting strategies are based on the intrinsic complexity of the questions. The problems are co-elaborated in the course of action by the expert and the caller and constituted as a domain of problems organized by one or more specific problems. This progressive elaboration aims at elucidating the problem situation implicitly contained in the initial request. Two individual instruments were developed within the shared database. Both of them showed transformation of the artifact structure. Moreover, a relation between the organized forms of hot-line assistance activity and the forms and functions of the instruments designed is identified: it may be fully or partially reciprocally congruent. These empirical results are discussed while opposing the ‘design-in-use’ criteria developed by operators to the ‘design-for-use’ criteria built up by the actors of institutional design. In conclusion, we emphasize points to consider in order to support further reflection on relations between use and design in an anthropocentric perspective.