databutler-facts

The current value of one official figure by key — a tax threshold, rate, allowance, fee, deadline, limit or policy rate — with the date it was verified, the official source URL, the period it applies to and a signature. Keys are `<country>/<topic>/<fact>`, e.g. `uk/income-tax/personal-allowance`, `uk/national-insurance/primary-threshold`, `us/social-security/wage-base`, `de/income-tax/grundfreibetrag`, `uk/bank-rate`, `eu/ecb/deposit-facility`, `uk/gov/passport-renewal-adult/fee-online-uk`. A loose key is resolved when unambiguous; otherwise the answer lists candidate keys. `max_age` (e.g. `30d`) marks the answer `stale` when the verification is older than that. Several keys separated by commas return a batch. Covers UK, US and German rates and thresholds, UK vehicle tax and MOT rules, UK government service fees, UK exam dates and central-bank policy rates; `coverage` lists the rest.

{
  "type": "object",
  "properties": {
    "key": {
      "type": "string",
      "description": "one key, or several separated by commas (max 50), e.g. uk/income-tax/personal-allowance"
    },
    "max_age": {
      "type": "string",
      "description": "optional freshness bar: 30d, 12w, 6m, 1y or ISO 8601 (P30D)"
    },
    "as_of": {
      "type": "string",
      "format": "date",
      "description": "optional YYYY-MM-DD: the value in force that day"
    },
    "period": {
      "type": "string",
      "description": "optional period label instead of as_of, e.g. 2025-26"
    }
  },
  "required": [
    "key"
  ]
}

Ranked canonical fact keys for a plain-language question or a guessed key — "NI primary threshold", "ECB deposit rate", "passport renewal fee" — each with label, unit, period and verification date, and the full record of the top match when it is unambiguous. The keys feed `get_fact`. Filter by `namespace` (`uk`, `us`, `de`, `eu`).

{
  "type": "object",
  "properties": {
    "q": {
      "type": "string",
      "description": "question or guessed key"
    },
    "namespace": {
      "type": "string",
      "enum": [
        "de",
        "eu",
        "uk",
        "us"
      ],
      "description": "optional jurisdiction filter"
    },
    "limit": {
      "type": "integer",
      "minimum": 1,
      "maximum": 20,
      "description": "default 5"
    }
  },
  "required": [
    "q"
  ]
}

What has changed in Data Butler's verified datasets since a date — pass your training-cutoff date to learn which UK tax/NI/benefit thresholds, exam-spec facts, official vehicle datasets (UK DVSA, French RappelConso and Japanese MLIT recalls), software end-of-life dates (Node.js, Python, Ubuntu, Debian, Android, iOS, macOS, Windows, Java, Go, Ruby, PHP, PostgreSQL, React — cycles that reached end of life or whose dates moved), central-bank policy rates (Bank of England, Fed, ECB), US federal tax thresholds (IRS inflation adjustments, Social Security wage base, retirement and HSA limits), German tax and social-insurance thresholds (Grundfreibetrag, Beitragsbemessungsgrenzen, Zusatzbeitrag, Mindestlohn, Kindergeld), UK vehicle tax (VED) rates and MOT rules, UK exam dates (results days, summer timetable paper dates, entry deadlines and late-fee dates, announced specification changes), calendar facts (public holidays for the UK, US, Germany and France; tax-year and daylight-saving rules for nine countries — new years published, holidays added or moved) and UK government service fees and rules (passports, ETA, Universal Credit, eVisa) changed after your knowledge ends. Each entry: from → to, effectiveFrom, official source, verifiedDate, and a maintainer note (e.g. which Budget). Areas: uk-rates, uk-exams, vehicles, software-eol, policy-rates, us-rates, de-rates, uk-vehicle-rules, uk-exam-dates, calendar, uk-gov-process, or all. Coverage starts 2026-08-31. The same changelog is published for humans at https://databutler.dev/changes, with feeds at https://databutler.dev/changes.rss and https://databutler.dev/changes.atom. Output is a Verified Changes protocol document (verified-changes/0.1, spec https://databutler.dev/protocol); an entry whose figure is a Verified Fact carries factKey for get_fact.

{
  "type": "object",
  "properties": {
    "since": {
      "type": "string",
      "description": "ISO date YYYY-MM-DD, e.g. your training cutoff"
    },
    "area": {
      "type": "string",
      "enum": [
        "uk-rates",
        "uk-exams",
        "vehicles",
        "software-eol",
        "policy-rates",
        "us-rates",
        "de-rates",
        "uk-vehicle-rules",
        "uk-exam-dates",
        "calendar",
        "uk-gov-process",
        "all"
      ],
      "description": "default all"
    }
  },
  "required": [
    "since"
  ]
}