The circulation of data ranked high among the objectives adopted by CGIAR at its founding in 1971. This chapter considers how agricultural experts attempted to realize a desired “full exchange of information” among scientists working at geographically distant sites, in different languages and cultural contexts, with different organisms and research interests from the 1970s to the early 2000s. The chapter focuses on the historical development of “crop descriptors,” today defined as providing an “international format and a universally understood language for plant genetic resources data.” Developers of descriptors aspire to agree on traits and terms that will allow users from diverse institutions and backgrounds to contribute to and extract information from an integrated data infrastructure. The chapter examines crop descriptors as a critical component of CGIAR’s earliest efforts to create “system-wide” research tools and agendas, emphasizing the scientific and political agendas that shaped this top-down systematizing work, finding that it provided an opportunity for CGIAR to instantiate and consolidate its central position in a web of international development initiatives.