Evidence syntheses that engage librarians as co-authors produce higher-quality results than those that do not. Trained as teachers, researchers, and information managers, librarians possess expert knowledge on research methodologies and information retrieval approaches that are critical for evidence synthesis. Researchers are under increasing pressure to produce evidence syntheses to inform practice and policymaking. Many fields outside of health science and medicine, however, do not have established guidelines, processes, or methodologies. This article describes how librarians led the creation of an interdisciplinary toolkit for researchers new to evidence synthesis. The implementation of the tools, including a protocol, supported eight evidence syntheses focused on effective agricultural interventions published in a special collection in Nature Research in October 2020. This article is a step-by-step overview of the tools and process. We advocate that librarian collaboration in evidence synthesis must become the norm, not the exception. Evidence synthesis project leads without access to a qualified librarian may use this toolkit as a point of entry for production of transparent, reproducible reviews.