Prime-factorize a positive integer (≤ 10^15 so the computation is always fast). Returns the prime factors with exponents, the divisor count, and whether n is prime.

Resolve a Unicode script name (loose matching) to its code point ranges, total size and a small sample. An unknown script is a successful `found:false`.

Convert between a spreadsheet column letter and its 1-based index in either direction. Provide exactly one of `letter` (e.g. "AA") or `number` (e.g. 27); the response always contains both.

Build an A1-style cell reference from 1-based row and column numbers, optionally marking the row and/or column absolute ($).

Parse an A1 range like "A1:C10" into its start and end cells (normalized so start is the top-left) and its extent — row count, column count and total cell count.

Name the interval between two notes (`to` at or above `from`) — its size in semitones, its diatonic number and its quality (perfect/major/minor/augmented/diminished). Correct spelling matters: C→F# is an augmented fourth, C→Gb a diminished fifth.

Build a chord from a root note and quality (major, minor, dim, aug, maj7, min7, dom7, dim7, half-dim7, sus2, sus4, maj6, min6). Notes are spelled by stacked thirds (C dom7 → C E G Bb). Returns the note names, MIDI numbers and semitone intervals.

Normalise an address to its canonical form — Ethereum to its EIP-55 checksummed form, bech32 Bitcoin to lowercase (base58check is left untouched as it is case-sensitive). An address that is not a valid address of a known chain is rejected before payment.

Transpose a note by a (possibly negative) number of semitones. Result is spelled chromatically with sharps, or flats when `preferFlats` is true.

Guess which chain an address belongs to from its shape and encoding, without requiring the caller to know it up front. Returns the chain, format and address type, or nulls when nothing matches.

Apply the EIP-55 mixed-case checksum to an Ethereum address, regardless of its input casing. Returns the checksummed address and whether it differed from the input. Non-hex input is rejected before payment.

Replace matches of a RE2 pattern with a replacement string. Replaces all matches by default (set all=false for first-only). The replacement may reference capture groups with $1, $2 or ${name}. Returns the resulting string.

Validate a number by the Luhn (mod-10) algorithm — the scheme behind credit/debit card numbers and many IDs. Spaces and hyphens are ignored. A mismatched check digit is a successful { valid: false }.

Test whether a RE2 pattern matches anywhere in the input. Returns { matched }. RE2 guarantees linear-time evaluation, so this is safe against catastrophic backtracking. An invalid pattern is a clean 400; no match is a successful 200.

Return both the fully-expanded (eight 4-hex groups) and canonical compressed (RFC 5952) forms of an address. IPv4 is returned unchanged in both fields.

Validate a Czech VAT (DIČ) number for a legal entity against the official register. Validity means the subject exists and is live in the VAT (DPH) register.

Compute the WCAG 2.1 contrast ratio between two colors and whether it passes AA/AAA.

Find the nearest CSS named color to a given color, by perceptual distance.

Decode a MessagePack or CBOR byte stream (supplied as a base64/base64url/hex string) back into a JSON value. A malformed envelope, malformed bytes, or a value that is not JSON-representable is rejected before payment.

Validate an ISBN-10 (mod-11, trailing X allowed) or ISBN-13 (GTIN mod-10) book number. Length after removing spaces/hyphens selects the scheme.