With the emergence of e-textbooks, along with expectations to integrate technology in instruction, teachers are becoming significant co-designers of the curriculum. Informed selection and sequencing of learning resources requires sensitivity to didactic nuance, and tools to support development and application of such sensitivity. Teachers' practices are constrained by the aspects of resources that are "searchable," which are limited using standard search engines, and the selection of tasks is influenced by the engines' ranking of search results, reflecting their popularity. We are developing and researching a coupled pair of tools to support mathematics teachers in making informed curricular decisions--a tool for tagging learning resources with prescribed categories of didactic metadata and a dashboard for browsing collections of resources according to this tagged metadata. In this article, we investigate affordances of these tools for the professional development of mathematics teachers--both practicing and pre-service teacher candidates. Viewing the dashboard, along with the metadata that it encodes, as a boundary object between the teachers' and the researchers' perspectives on curricular design, we show how teachers learned through acts of boundary crossing, conceived as transitions and interactions between the two communities' curricular discourses. We show how using the dashboard in a task-selection assignment encouraged teachers to reflect on their practice--making explicit the tacit considerations that they apply to curricular decisions and articulating them from the researchers' perspective. We also describe the emergence of "hybrid" search strategies, integrating multiple perspectives to create practices that are both didactically informed and practically relevant for instruction.