Attempting to speak usefully to vague generality... if your functions are returning different concrete monadic values you need to either run them and get something pure out or translate them into your current context. It's usually better practice, however, to leave the choice of monad up to the call site and only ask for the interfaces you need (MonadState, MonadReader, etc), at which point there's no call-site-local translation needed at all, you just have to make sure you're supporting the interfaces requested.