Government & Open Data

Pull official statistics from the World Bank and Eurostat keyless. The mistakes this prevents: quoting a GDP figure from training memory when the real series is one call away, and the two structural traps - World Bank's off-by-default JSON and its indicator-code lookup step - that make first attempts fail.

Ranked APIs

1. World Bank Indicators (api.worldbank.org/v2) - DEFAULT. ~1,400 indicators × every country × back to 1960. No key. The catch: you query by opaque indicator code (NY.GDP.MKTP.CD), so the lookup step below is mandatory for unfamiliar metrics.
2. Eurostat (ec.europa.eu/eurostat/api) - EU-official statistics when the user wants the EU source of record or EU-only granularity. No key, JSON-stat format (denser to parse - shape below).

Procedure

1. Resolve the indicator code first. Verified ones to use directly: NY.GDP.MKTP.CD (GDP, current US$), SP.POP.TOTL (population), SP.DYN.LE00.IN (life expectancy), FP.CPI.TOTL.ZG (inflation %), SL.UEM.TOTL.ZS (unemployment %). Anything else: search https://api.worldbank.org/v2/indicator?format=json&per_page=50&source=2 filtered client-side, or hit /v2/indicator/{guess}?format=json to confirm a code exists before building the real query. Never invent a code - a bad code returns an error object inside a 200. Emissions codes (EN.ATM.CO2E.PC, EN.GHG.*) are served from a chronically failing backend - expect 502s/hangs and fall back to Eurostat (env_air_gge) for EU countries rather than retry-looping.
2. Always append format=json. The World Bank default is XML; forgetting this is the #1 failure.
3. Prefer mrv=N over date= for "latest" queries. mrv=10 (most recent 10 values) hits the API's cache and skips the null-trimming problem; date= ranges on less-trafficked indicators frequently hang or 502 where the same indicator's mrv query answers instantly.
4. Handle nulls. Recent years are often null (reporting lag ~1-2 years); the latest published value is not the latest year. Report the year you actually used.
5. Compare countries in one call with country/US;CN;DE/... (semicolon-separated ISO codes), not N calls.

Ask the user only if missing: countries (no default), metric (no default), years (default: last 10 published).

URL templates + real response shapes

Indicator series:

https://api.worldbank.org/v2/country/US/indicator/SP.POP.TOTL?format=json&mrv=10
https://api.worldbank.org/v2/country/US;CN;DE/indicator/NY.GDP.MKTP.CD?format=json&mrv=1&per_page=100
https://api.worldbank.org/v2/country/US/indicator/SP.POP.TOTL?format=json&date=2013:2022   ← explicit range

[{"page":1,"pages":1,"per_page":50,"total":1,"lastupdated":"2026-07-01"},
 [{"indicator":{"id":"SP.POP.TOTL","value":"Population, total"},
   "country":{"id":"US","value":"United States"},
   "date":"2022","value":333996304,"unit":"","obs_status":""}]]

Gotchas: the top level is a two-element array - [0] is paging metadata, [1] is the data (or null when the query matched nothing - check before iterating). Rows are newest-first. value: null means not-yet-reported. Default page size is 50 - set per_page on multi-country/multi-year pulls.

Country metadata (income level, region, capital):

https://api.worldbank.org/v2/country/JPN?format=json

[1][0] carries incomeLevel.value ("High income"), region.value, capitalCity. Aggregates like "European Union" have region.id: "" - filter them out of per-country rankings.

Eurostat:

https://ec.europa.eu/eurostat/api/dissemination/statistics/1.0/data/{dataset}?format=JSON&geo=DE&time=2023

Example dataset: tps00001 (population). Response is JSON-stat: values live in value keyed by a flat index ({"value":{"0":83118501}}), decoded via dimension.{geo,time}.category.index. With one geo and one time filter, index "0" is your number; for anything multi-dimensional, filter server-side (&geo=DE&geo=FR) to keep the index math trivial. Find dataset codes by searching "eurostat" + the metric name; the code is in the dataset's URL on the Eurostat site.

Deliverable

The series or comparison as a small table - country × year × value with units and the indicator's full name - plus the exact URL used and the lastupdated date, with any null years called out.

Do NOT use - reach for X instead

• US Census API (api.census.gov) - every endpoint now requires a key (free signup, but it cannot be liveness-verified keyless, so it ships as a pointer only: sign up, then get=NAME,B01001_001E&for=state:*&key=... on the ACS datasets).
• data.gov CKAN API (catalog.data.gov/api/3) - returns 404 on every action endpoint, verified. Use each agency's own API instead of the catalog.
• Static country facts (capital, currency, flag, language) - geo-places; this skill is time-series statistics.
• Live market prices, FX - finance-fx.
• OECD/IMF deep dives - out of pack scope; World Bank mirrors most headline series, name it as the tradeoff.

Quality bar

• No indicator code was invented; unfamiliar metrics went through the lookup step.
• [1] === null and value: null handled; the reported year is the year of the data.
• Statistics come from the API response, never from training memory - with lastupdated quoted.
• A 502 or hang produced one mrv retry or an Eurostat fallback, not a retry loop.

Sourced and liveness-verified from the public-apis project (MIT).