Browse the Federal Reserve FRED category tree to DISCOVER economic series. Pass a categoryId to get that category (name + parent), its child categories, and the most-popular series filed under it (id, title, units, frequency) — then pull the data with econ.fred. Omit categoryId (or pass 0) for the eight top-level categories: Money/Banking/Finance, Population/Employment/Labor, National Accounts, Production & Business Activity, Prices, International Data, U.S. Regional Data, Academic Data. Walk down via each child's id. Free, public-domain (FRED). The structured map of what FRED actually contains — far more reliable than guessing series ids. Companion to econ.fred (fetch/search) and econ.fred-releases (calendar).