Numerous toolkits have been developed to support ethical AI development. However, toolkits, like all tools, encode assumptions in their design about what work should be done and how. In this paper, we conduct a qualitative analysis of 27 AI ethics toolkits to critically examine how the work of ethics is imagined and how it is supported by these toolkits. Specifically, we examine the discourses toolkits rely on when talking about ethical issues, who they imagine should do the work of ethics, and how they envision the work practices involved in addressing ethics. We find that AI ethics toolkits largely frame the work of AI ethics to be technical work for individual technical practitioners, despite calls for engaging broader sets of stakeholders in grappling with social aspects of AI ethics, and without contending with the organizational and political implications of AI ethics work in practice. Among all toolkits, we identify a mismatch between the imagined work of ethics and the support the toolkits provide for doing that work. We identify a lack of guidance around how to navigate organizational power dynamics as they relate to performing ethical work. We use these omissions to chart future work for researchers and designers of AI ethics toolkits.