World Bank Open Data — fetch a time series of a specific indicator for a country (or 'all'). 1000+ indicators across 200+ countries, many series going back to 1960. Indicator codes are dotted-token strings, e.g., NY.GDP.MKTP.CD (GDP current US$), SP.POP.TOTL (population total), FP.CPI.TOTL.ZG (inflation CPI annual %), SL.UEM.TOTL.ZS (unemployment %), SE.ADT.LITR.ZS (adult literacy %), SP.DYN.LE00.IN (life expectancy). Country = ISO 2-letter (e.g., US, CN), ISO 3-letter (USA, CHN), or 'all'. Optional yearFrom/yearTo bracket. Each observation: country id+name, year, numeric value (may be null for missing), obsStatus. Returns indicator name + total count + pagination metadata.