Many digital libraries have identified learners as a core audience. Indeed, many of their resources can be reused in educational contexts. Nevertheless, the search criteria used for retrieving texts as a specific multimedia type are limited. They often do not include properties specific to educational contexts. Assigning LOM metadata to a theatre play or a painting is difficult, since it was not created for a particular learning context. However, it is possible to assign metadata to textual resources based on their characteristics and map these characteristics to an IEEE LOM or DCMI Audience metadata element. Text readability metrics for instance can be mapped to educational audiences. In the scope of the iCase project, we are developing an assessment item generation system. We have therefore analyzed metadata models for assessment resources and defined a set of metadata which should be assigned to the multimedia components of assessment items. A major challenge consists in relating multimedia resources to the specific audience metadata. In order to include external resources such as texts, we developed a component available as a Web service to assign metrics related to text readability. In this paper, we present metadata for assessment items and introduce readability metrics.