Look up ISO 3166-2 subdivisions (states, provinces, regions). Pass code (e.g. US-CA) to resolve a single subdivision → name + country, or country (2-letter ISO 3166-1, e.g. US) to list all of that country's subdivisions with their codes. Bundled authoritative ISO 3166-2 data (~3.8k subdivisions across 237 countries) — the address/jurisdiction ground truth an LLM hallucinates codes for.