What tool of monetary supply is the interest rate the Fed charges on loans to financial institutions?

The interest rate that the Federal Reserve (Fed) charges on loans to financial institutions is known as the discount rate. It serves as a key tool of monetary policy, influencing the cost of borrowing for banks and, consequently, impacting overall money supply and lending in the economy. By adjusting the discount rate, the Fed can control liquidity in the financial system, thereby influencing economic activity and inflation rates.