EU VAT number validation for agents: per-country format rules and check-digit algorithms (DE, ES, FR, IT, NL, PT, BE, AT, PL, SE...) executed offline — deterministic, no VIES dependency, instant JSON verdict with country and normalized number. $0.001 USDC via x402 on Base. SYNTHORA. First 3 calls FREE per wallet — send header X-WALLET: 0x<addr>. No charge on upstream failure.