Verified Facts — official thresholds, rates and fees with source, date and signature

Look up an official figure by key and get back the value, its official source URL, the date a human verified it, a fresh/stale flag against your max_age, and an Ed25519 signature you can check against databutler.dev/.well-known/jwks.json. 496 keys: UK tax and benefits, US federal thresholds, German tax and social insurance, EU figures. Tools: get_fact (key + max_age), resolve_fact (plain-language question to key), what_changed_since (facts that changed after a date, e.g. your training cutoff). O