User story ambiguity has been identified as a serious challenge in Requirements Engineering (RE) due to various linguistic and contextual constraints. These challenges have been addressed by research employing mainly Natural Language Programming (NLP) techniques and Conceptual Modeling. However, existing studies have only limitedly investigated the impact of personal and organizational elements on user story ambiguity and user awareness of ambiguity issues. Therefore, this research aims to mitigate user story ambiguity by developing a knowledge repository for user story writing from different domains. To do so, we aim to investigate the role of cognitive elements to enhance user story clarity. Technically, the use of context-free grammar will be investigated to maintain the quality of the knowledge repository. Finally, for raising awareness of ambiguity issues, gamification concepts (e.g., levels/tags, points) will be applied to monitor user progress.