As the Model Driven Development (MDD) and Product Line Engineering (PLE) appear as major trends for reducing software development complexity and costs, an important missing stone becomes more visible: there is no standard and reusable assets for packaging the know-how and artifacts required when applying these approaches. To overcome this limit, we introduce in this paper the notion of MDA Tool Component, i.e., a packaging unit for encapsulating business know-how and required resources in order to support specific modeling activities on a certain kind of model. The aim of this work is to provide a standard way for representing this know-how packaging unit. This is done by introducing a two-layer MOF-compliant metamodel. Whilst the first layer focuses on the definition of the structure and contents of the MDA Tool Component, the second layer introduces a language independent way for describing its behavior. An OMG RFP (Request For Proposal) has been issued in order to standardize this approach.