These standards could be based, for example, on supervisory ratings. They are necessary to prevent the window from so being used to enable weak banks to avoid market disruption. Banks that met the threshold could borrow without the use of the funds.
The open market desk can offset this effect by draining reserves from the system. But the amounts that banks choose to borrow at the discount window can be difficult to predict, complicating the management of the federal funds rate, especially when borrowings are large.