After more research, I've realized that returning a direct output string fundamentally goes against how SK is designed. SK is intended to call any necessary functions as needed (sometimes multiple functions), and pull that information together for it's output.

For the use case I mentioned, it's better to use agents, and ask the first agent which function to call. Then You can execute that method manually by calling a switch-statement or similar.

I do still wish SK had a setting to only do the method selection and return the exact output string, but it seems like it's almost an entirely different product.