Plus code (Open Location Code) encoder and decoder

Plus code (Open Location Code) encoder and decoder: encode coordinates as a plus code at a chosen length, or decode a full code back to its bounding box and centre. Also shortens a full code against a reference coordinate and recovers a shortened code given a reference, which is how plus codes are normally exchanged in text. Returns code length, precision in metres and validity.

Output (data): code, length (integer|null, null for an invalid code), bbox {min_lat, min_lon, max_lat, max_lon}, center {lat, lon}, precision_m (cell height in metres, rounded to 0.1), is_full, is_short, valid, reason (string|null, null on success). Invalid codes on op=decode return 200 with valid:false and a reason (invalid character is checked before the + position); short codes decode to valid:true, is_short:true without a bbox. shorten also returns full_code. shorten/recover with a malformed code are 400 INVALID_PARAM.

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#geo-pluscode