In this perspective, the authors critically examine "rater training" as it has been conceptualized and used in medical education. By "rater training," they mean the educational events intended to "improve" rater performance and contributions during assessment events. Historically, rater training programs have focused on modifying faculty behaviours to achieve psychometric ideals (e.g., reliability, inter-rater reliability, accuracy). The authors argue these ideals may now be poorly aligned with contemporary research informing work-based assessment, introducing a compatibility threat, with no clear direction on how to proceed. To address this issue, the authors provide a brief historical review of "rater training" and provide an analysis of the literature examining the effectiveness of rater training programs. They focus mainly on what has served to define effectiveness or improvements. They then draw on philosophical and conceptual shifts in assessment to demonstrate why the function, effectiveness aims, and structure of rater training requires reimagining. These include shifting competencies for assessors, viewing assessment as a complex cognitive task enacted in a social context, evolving views on biases, and reprioritizing which validity evidence should be most sought in medical education. The authors aim to advance the discussion on rater training by challenging implicit incompatibility issues and stimulating ways to overcome them. They propose that "rater training" (a moniker they suggest be reserved for strong psychometric aims) be augmented with "assessor readiness" programs that link to contemporary assessment science and enact the principle of compatibility between that science and ways of engaging with advances in real-world faculty-learner contexts.