Three textbook baseline forecasts: mean (forecast = average of history), naive (forecast = last value), drift (linear extrapolation from first to last point). Use as a sanity floor - any sophisticated method (SES, Holt, Holt-Winters) should beat the best of these on a backtest, otherwise the extra complexity isn't earning its keep. Returns point forecasts + 95% prediction intervals per Hyndman §3.1.

Great-circle distance between two latitude/longitude points using the haversine formula. Returns kilometers and miles. Deterministic.

Hex encode or decode text. mode: encode (default) or decode.

Simple exponential smoothing (SES) - level-only forecast for series without trend or seasonality. Higher alpha (closer to 1) tracks recent values aggressively; lower alpha (closer to 0) smooths through noise. Default alpha=0.3 is a common conservative pick; pass an explicit alpha or use forecast-eval to pick the one that minimizes backtest error. Forecast is flat (= last fitted level) for all horizons.

Greatest common divisor and least common multiple of two or more integers, computed exactly (arbitrary precision). Useful for cycle alignment, scheduling periods and fraction work. Signs are ignored; a zero makes the LCM zero. Results beyond 2^53 come back as strings so no digit is lost.

HMAC signature of a message with a shared key. Algorithms: sha256 (default), sha512, sha1. Returns hex and base64.

Decompress a base64-encoded gzip payload. Returns the result as utf8 (text) or base64 (binary). Refuses to expand past 10MB to defend against zip bombs.

Holt's linear trend method - level + trend (no seasonality). Two smoothing parameters: alpha (level) and beta (trend). Forecast extrapolates as a straight line from the last fitted level along the last fitted trend, so it grows or shrinks linearly with horizon. Use this when your series has a persistent up/down trend but no seasonal cycle (e.g. a SaaS MRR climb, a deflating cohort retention curve).

Encode text to HTML entities or decode them back. mode: encode (default) or decode.

Validate, pretty-print (any indentation, 0-8 spaces), or minify JSON, optionally with object keys sorted. canonical: true returns the RFC 8785 (JCS) canonical form - keys sorted, no whitespace, ECMAScript number and string serialization - plus its SHA-256, for hashing and signing. Numbers are read as IEEE-754 doubles and a duplicate key keeps its last value. Returns parse errors with position when invalid.

Extract <title>, <meta description>, OpenGraph/Twitter cards, canonical URL, and JSON-LD blocks from an HTML string. Distinct from /api/meta which fetches a URL - feed this the HTML you already have (from /api/render, /api/extract.body, or your own fetch).

Enumerate every <a href> in an HTML string with its anchor text and rel attribute. Optionally resolves relative hrefs against a base URL and filters by a regex on the href. The deterministic way to crawl a page's outlinks without writing a regex.

Deep-compare two JSON values. Returns a list of changed/added/removed paths (capped at 1000 differences).

Get the ISO 8601 week number, ISO day-of-week, quarter, and day-of-year for any date. Useful for fiscal/reporting calendars, weekly aggregations, and sprint planning.

Flatten nested JSON to dot-path keys, or unflatten dot-path keys back to nested JSON. mode: flatten (default) | unflatten.

Compute the internal rate of return (IRR) of a cashflow stream - the discount rate at which NPV = 0. Index 0 is treated as t=0 (typically the negative initial investment); indices 1..n are inflows in subsequent periods. Solved via Newton-Raphson with bisection fallback. Requires at least one positive and one negative cashflow (otherwise IRR is undefined). Multiple sign changes in the cashflows can produce multiple IRR roots - we return the first one found.

Convert an HTML fragment or document you already have into clean markdown. (To fetch + convert a live URL, use /api/extract.)

Validate an IBAN: country code, length, and the ISO 13616 mod-97 checksum.

Fit a least-squares line y = slope·x + intercept to two equal-length series. Returns slope, intercept, r² (variance explained), and optionally predicted y values for new x inputs - useful for trend extrapolation (e.g. project next quarter's revenue from the last 8 quarters).

Compute the monthly (or per-period) payment on a fully-amortizing loan: mortgage, auto, student loan, business loan. Returns the periodic payment, total paid over the term, and total interest. Matches Excel's PMT(rate, nper, -principal). Use this when you just need the payment number, not the full per-period schedule (see amortization).