Which government agency primary mission is ensuring that enough money and credit are available to sustain economic growth without causing inflation

Federal Reserve

Explanation:

The Federal Reserve is the government institution responsible for monetary policy in the United States, which controls the amount of money and credit in circulation in the economy. The Federal Reserve's mission, therefore, is to ensure the proper conditions for the macroeconomic environment for businesses to prosper in a sustainable manner, raising the level of the American economy. This is done through monetary policy.

The answer is The Federal Reserve System or "FED".