Headline central-bank policy/benchmark rates side-by-side in one call, normalized: US (Fed effective funds rate), Euro area (ECB deposit facility rate), Japan (BoJ call-money benchmark), United Kingdom (SONIA, which tracks the BoE Bank Rate). Each result names the bank, country, the rate, the as-of date, the FRED series id, and a label stating exactly which instrument it is (banks don't all publish the same policy instrument). Pass bank to filter (one of: fed, ecb, boj, boe), or omit for all. Source: FRED (St. Louis Fed).