String similarity: Levenshtein, Jaro-Winkler distance and Soundex/Metaphone phonetic keys

String similarity: compare two strings and return every standard measure in one call: Levenshtein and Damerau-Levenshtein edit distance, normalised similarity, Jaro and Jaro-Winkler, longest common subsequence, Dice coefficient on character bigrams, and the Soundex, Metaphone and NYSIIS phonetic keys of each string. Optional case folding, accent folding and whitespace normalisation before comparison.

Output (data): levenshtein, damerau_levenshtein, normalised_similarity (0-1), jaro, jaro_winkler, lcs_length, dice, phonetic {a: {soundex, metaphone, nysiis}, b: {...}} (Soundex, Metaphone and NYSIIS are computed exactly as the jellyfish library does, on the folded string; with only=soundex|metaphone|nysiis just that key), equal_after_fold, folded {a, b}.

Deterministic: identical input returns identical output, so the response is served with Cache-Control: private, max-age=31536000, immutable (the paying client may cache it indefinitely; shared caches must not, because the response is paid).

Price: $0.05 USDC per call (x402, Base). Route contract version 1.0.0. Docs: https://api.duoleads.com/docs#text-similarity