The contribution presents a reflection on the relationship between the use of assessment tools and the two-sided phenomenon of the completion rate and dropout rate in MOOCs. In support of this reflection, the experience of the MOOCs proposed by the University of Modena and Reggio Emilia (UNIMORE) within the EduOpen network is described. In particular, the data relating to the quantity and quality of the assessment tools used in the MOOCs UNIMORE and the data on the completion rates of the 5 pathways currently active in the training offer on EduOpen and, specifically, of a MOOC with a complex evaluation system and particularly high completion rates are reported.