First, governments should pay the market price for resources that they seek to use for public policy purposes. This means borrowing in the market (if borrowing is needed) at the market rate, not at an artificially reduced rate from banks or the central bank. (This is, of course, a key element of central bank independence.
A central bank can't seriously hope to run an independent monetary policy if the demands of government finance dominate its balance sheet.) For markets to be able to price government borrowing properly, they need some information about governments' intentions – a degree of fiscal transparency is required.