Pick a channel, any channel.

Monetary economists have been researching the sources and consequences of monetary non-neutrality for fifty years.

All you need is an upward-sloping Phillips Curve. But if you want something more mechanical, I can give you that.

I don't have to talk about bank lending, though I can (Kashyap and Stein 2000).

I don't have to talk about lending overall, though I can (Bernanke Gertler Gilchrist 1999, Carlstrom and Fuerst 1997, Oliner and Rudebusch 1996)

I could just talk about upward-sloping Phillips Curves and nominal price stickiness (Gali and Gertler 1999).

I could talk about exchange-rate devaluation as a channel of monetary policy effectiveness (Svensson).

I could talk about high-frequency identification of monetary non-neutrality (Nakamura and Steinsson; Gertler and Karadi).

I could talk about event-based identification of non-neutrality (Romer).

I don't have to talk about recent events, but I can (Gertler, Karadi, Jermann, Quadrini, and Kiyotaki all have recent papers on non-neutralities even at the zero lower bound).

All of these papers identify short-run monetary non-neutralities; that is, monetary policy affects output. The best-identified papers identify the most non-neutrality, that is, that monetary policy affects real variables in a quantitatively significant way in the short run.

There's a nominal spending channel; a bank lending channel; a broad credit channel; an exchange-rate channel; a wealth channel; an expectations channel; and a traditional interest rate channel. How many channels do you really need?

I could even talk more broadly about instruments and goals. One natural division of labor is to use monetary policy to fix recessions, which are essentially monetary phenomena, and use fiscal policy to fix public goods and social insurance distortions. Choose fiscal policy on public finance grounds, and choose monetary policy to fix recessions.

I hate to rest on authority, but there's a reason that macroeconomists have put so much more energy into monetary policy design than fiscal policy design when it comes to recession-fighting.