Synthetic immunity to cancer has been pioneered by the application of chimeric antigen receptor (CAR) engineering into autologous T cells. CAR T cell therapy is highly amenable to molecular engineering to bypass barriers of the cancer immunity cycle, such as endogenous antigen presentation, immune priming, and natural checkpoints that constrain immune responses. Here, we review CAR T cell design and the mechanisms that drive sustained CAR T cell effector activity and anti-tumor function. We discuss engineering approaches aimed at improving anti-tumor function through a variety of mechanistic interventions for both hematologic and solid tumors. The ability to engineer T cells in such a variety of ways, including by modifying their trafficking, antigen recognition, costimulation, and addition of synthetic genes, circuits, knockouts and base edits to finely tune complex functions, is arguably the most powerful way to manipulate the cancer immunity cycle in patients.