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Apply an RFC 6902 JSON Patch to a JSON document and return the result. An invalid or unresolvable patch (e.g. a failed `test`, or a path that does not exist) is rejected before payment.

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.

Poisson distribution with rate `lambda` (> 0, ≤ 1e9). `function` selects the mass (pmf), cumulative distribution (cdf) or quantile / inverse-CDF.

Render text (URL, vCard, Wi-Fi config, …) as a QR code — SVG string or PNG data URL.

Area (shoelace formula), perimeter and centroid of a simple polygon given its vertices in order. Vertices are treated as a closed ring (last connects to first).

The n-th Catalan number Cₙ = C(2n, n)/(n+1), counting balanced bracketings, binary trees, and many other structures. Requires n ≤ 10000.

Jaro similarity and the Jaro-Winkler variant (which boosts scores for a shared prefix), both in [0,1]. The prefix boost factor is configurable (default 0.1, max 0.25). Well suited to short strings like names.

Generate an RFC 4226 counter-based HMAC one-time password from a base32 secret and counter. Configurable digits (6–10, default 6) and algorithm (SHA1/SHA256/SHA512, default SHA1). An invalid base32 secret is a clean 400.

Balance an equation such as "H2 + O2 -> H2O" into the smallest whole-number coefficients using exact rational linear algebra. Equations that cannot be balanced with positive coefficients are clean 400s.

Transcode a document between json, json5, jsonc, yaml, xml, csv, tsv, toml, ndjson, ini, env, properties, plist and querystring. Any source converts to any target through a JSON hub. Malformed input or a target that cannot represent the structure is rejected before payment.

Given a reaction and a known amount (moles or grams) of one species, compute the amount of a target species. The equation is balanced automatically.

Count the LLM tokens in text for a given model or encoding — exact for OpenAI and open models (Llama, Mistral, Qwen, Gemma, DeepSeek, Command-R); labelled-approximate for Claude & Gemini.

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

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.

Student's t distribution with df degrees of freedom (> 0). `function` selects the density (pdf), cumulative distribution (cdf) or quantile / inverse-CDF.

Future value of a present sum and/or a level annuity, given a per-period rate and number of periods. Set dueAtBeginning=true for an annuity-due (payments at the start of each period).

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.

Test whether a coordinate falls inside a polygon.

Return the antonyms (opposites) of an English word, aggregated across all its senses. Optionally filter by part of speech. An unknown word returns found:false with a 200.

Encode a word with the Metaphone algorithm — more accurate than Soundex for English pronunciation.

Detect whether a User-Agent belongs to a known bot, crawler, AI agent or HTTP tool, and if so return its name and category (search, social, seo, ai, monitoring, tool, …).

Render GitHub-Flavored Markdown to HTML. Output is sanitized by default (scripts, event handlers and javascript: URLs removed); set sanitize=false to keep raw HTML.

Resolve a Unicode block name (loose matching) to its range, size, count of assigned characters and a small sample. An unknown block is a successful `found:false`. This is a Unicode Character Database block — not a blockchain block.

Look up an active ISO 4217 currency by its alphabetic code or numeric code. Provide exactly one field. Returns the code, numeric code, name and number of minor units (decimal places).