Two dimensions of tele-learning project are concerned by this article where we take in consideration learning, teaching and specific learning context. We believe that we have to accord particular attention to improve some cognitive and socio-cognitive skills such negotiation, argumentation and knowledge restructuring. We propose a pedagogical structure of mediation within mediated and distributed learning environments. At the same time, we suggest an on-line tool for pedagogical scenario to teacher. The tool allows teacher to adopt different approaches where learning products are related to the best teaching and learning strategy to be used. The tool also offers a set of job-aids that help teacher to manage, specify and develop learning activity, assessment modality, etc.