We investigate pre-service teachers’ learning to plan discussions promoting students’ mathematical reasoning. Specifically, we analyse opportunities to learn to plan provided by three planning tools: a conceptual framework of the mathematical work of reasoning and proving, a set of talk moves, and a mathematical task with students’ work. In learning cycles, the pre-service teachers investigated, planned, enacted, and reflected on practice, using role-plays as an approximation to practice. The planning was organised in small groups, and these groups’ collaborative work was videotaped, transcribed, and analysed using thematic analysis. Our findings reveal three patterns of tool use: tools as a support for planning, planning as a context to make sense of the tools, and the use of talk moves to plan when the students’ work was insufficient as a support. From these patterns, we identify several opportunities to learn afforded by the tools. However, we also identify and discuss limitations in the design of the tools, particularly related to mathematical reasoning. Based on our findings, we discuss implications for teacher education.