The mobile agent technology provides facilities that enable to reduce the complexity of telecommunication services development. However the major part of this development is still devoted to the code production. In order to optimize the development of services, this production should be reduced while the main part must become an upstream activity, i.e., the elaboration of specifications. This paper introduces an Architecture Description Language (ADL) devoted to the design of mobile agent systems to be implemented in a MASIF compliant platform. The ADL is defined as a UML profile called the MASIF-DESIGN profile. It enables the designer to describe the platform he/she uses, to locate the agents in the platform and to define the elements required from the platform for the achievement of the distribution transparencies.