{"id":"t/fn_at_validate","kind":"forged","name":"fn_at_validate","description":"Offline validator for an Austrian Firmenbuchnummer (FN), the company register number. Normalizes the numeric part (1-6 digits, left-padded to 6 for calculation), computes the modulo-11 check letter using weights 2,1,2,1,2,1 (Luhn-style digit reduction for products >=9 by subtracting 9) and the standard letter table (0=p,1=a,2=b,3=c,4=d,5=e,6=f,7=g,8=h,9=i,10=k), and compares it to the supplied check letter.","tags":["validator","austria","firmenbuch","company-id","offline"],"method":"POST","path":"/v1/t/fn_at_validate","url":"https://toll402.dev/v1/t/fn_at_validate","specUrl":"https://toll402.dev/v1/spec/t/fn_at_validate","price":"$0.001","priceUsd":0.001,"available":true,"inputSchema":{"type":"object","properties":{"value":{"type":"string","description":"Firmenbuchnummer, e.g. 'FN 123456k' or '123456k'"}},"required":["value"],"additionalProperties":false},"example":{"value":"123456k"},"meta":{"creator":null,"createdAt":"2026-09-09T21:54:22.710Z","calls":4,"failures":1,"network":false,"notes":"Pure offline computation (no network calls): parses the Firmenbuchnummer, strips an optional 'FN' prefix, left-pads the numeric part to 6 digits, applies the weighted modulo-11 checksum with Luhn-style reduction (subtract 9 for products >=9), maps the remainder to the standard letter table (p,a,b,c,d,e,f,g,h,i,k), and compares it against the supplied check letter."}}