This paper introduces the MarkTool System — a software system designed to support formative assessment of open-ended written assignments. The MarkTool System brings together services from conventional Learning Management Systems, a marking application and other specialized tools to facilitate the formative assessment of open-ended written assignments. MarkTool System uses the services provided by the university?s Learning Management System for assignment submission and returning of the marked assignments. It provides an onscreen marking tool which allows users to mark open-ended written assignments using their paper-based assessment skills. MarkTool System also supports the concepts of self-assessment and peer-assessment, assessment related discussion, quality/consistency control of feedback, and analysis of assessment results.