Of course, such rules are based on rather strong assumptions and simplifications and thus do not play a major role in policy decisions; no real policy-maker just looks at two or three variables. Moreover, the estimated coefficients are a combination of policy preferences and structural features of the economy and thus are difficult to interpret.
Nevertheless, as this tool is widely used and assuming that it is able to broadly capture some statistical regularities of policy-making, let me make three remarks. First, such reaction function estimates are surrounded by considerable uncertainty and show very wide variations across different specifications.