With the help of two examples, we illustrate the usefulness of agent-based models as a tool for economic policy design. In our first example, we apply a financial market model in which the order flow of speculators, relying on technical and fundamental analysis, generates intricate price dynamics. In our second example, we apply a Keynesian-type goods market model in which the investment behavior of firms, relying on extrapolative and regressive predictors, generates complex business cycles. We add a central authority to these two setups and explore the impact of simple intervention strategies on the model dynamics. Based on these experiments, we conclude that agent-based models may help us to understand how markets function and to evaluate the effectiveness of various stabilization policies.