State capacity to provide public services depends on the motivation of the agents recruited to deliver them. We design an experiment to quantify the effect of agent selection on service effectiveness. The experiment, embedded in a nationwide recruitment drive for a new government health position in Zambia, shows that agents attracted to a civil service career have more skills and ambition than those attracted to “doing good”. Data from a mobile platform, administrative records, and household surveys show that they deliver more services, change health practices, and produce better health outcomes in the communities they serve.