{"name":"luhn","title":"Luhn Checksum (validate / check digit)","category":"developer","description":"Validate a Luhn number (cards, IMEI) or compute its check digit. Formula only — not card validity.","price_usd":0.001,"input_schema":{"type":"object","properties":{"number":{"type":"string","description":"Number to check (non-digits ignored)"},"mode":{"type":"string","description":"Operation","enum":["validate","check_digit"]}},"additionalProperties":false,"required":["number"]}}