Purpose: This paper explores the challenge of "fuzzy" assessment criteria and feedback with a view to aiding student learning. The paper untangles three guiding principles as mechanisms to enhance the effectiveness of assessment and feedback through overcoming the inherent challenges which stem from tacit judgement during assessment. Design/methodology/approach: The paper applies a realistic evaluation methodology, with a framework for assessment and feedback consisting of three principles -- Means, Opportunity and Motivation (MOM). Through in-depth interviews with undergraduate and postgraduate management students the paper identifies how and when the means, opportunity and motivation principles impact student learning through assessment and the utility of the feedback received on their learning. Findings: The findings in the paper illustrate that students do not always understand the feedback they receive on their learning because they do not fully understand the criteria to which it refers due to the tacit dimensions of assessment. The findings substantiate the proposition that effective assessment processes must ensure that students have the means, opportunity and motivation to use feedback and to understand the criteria, a central component of which is understanding tacit dimensions of assessment. Practical implications: The paper deciphers three practical implications for instructors related to (1) teaching, (2) course and program design and (3) the nature of the feedback instructors should provide. Originality/value: While prior scholarship has flagged the challenge of "fuzzy" assessment and feedback, this paper identifies when and how the means, opportunity and motivation principles are manifested in the process of making the tacit components of assessment codified and actionable, a critical process in developing expert learners.