# openfang-rail

> Deterministic business-identifier validation (IBAN, LEI, VAT, UK company number) and rental due-diligence (deposit-safety, listing-risk, one signed verdict), paid per call via x402 (gasless EIP-3009 USDC on Base). Zero custody, signed receipts, offline + explainable (no ML, no scraping). First 20 calls/day free.

## For agents
- Discover: GET /.well-known/mcp.json and /.well-known/x402.json
- MCP: POST /mcp (JSON-RPC 2.0: initialize, tools/list, tools/call)
- REST: POST /v1/tools/{tool}/call with body {"input":{ … }} (see each tool's input_schema in mcp.json)
- Free tier first; then a 402 challenge — sign an EIP-3009 voucher, retry with X-PAYMENT.
- Every result carries a signed XDR-1 receipt; recover the signer to verify offline.

## Tools
- iban-check: Validate an IBAN by ISO 13616 structure and MOD-97-10 checksum (offline, no bank lookup).
- lei-check: Validate a Legal Entity Identifier (ISO 17442 + ISO 7064 MOD-97-10 check digits).
- vat-mod97-check: Structural VAT check (BE mod-97 family).
- company-number-format: Validate UK Companies House number format (not existence).
- rent-deposit-guard: Rental deposit safety: IBAN checksum + property/deposit country alignment + pre-viewing flag.
- rental-listing-risk: Explainable rental-fraud risk score over listing red-flag signals (deterministic rule engine).
- rental-verdict: One combined, signed rental due-diligence verdict: deposit + landlord entity (LEI/company) + listing risk.
- batch-validate: Run up to 50 identifier checks (IBAN / LEI / VAT / UK company / SWIFT / ABA / EIN / IFSC / ABN / Luhn / ISBN / E.164 / SEDOL) in ONE paid call: one voucher, one settlement, one signed XDR-1 receipt covering the whole batch. Flat price regardless of count — at 50 items, 10x cheaper per check than single calls.
- swift-bic-check: Validate a SWIFT/BIC code by ISO 9362 structure (bank code, ISO country, location, optional branch).
- aba-routing-check: Validate a US ABA routing number by its (3,7,1)-weight mod-10 checksum.
- ein-format-check: Validate US Employer Identification Number FORMAT (NN-NNNNNNN). No public EIN checksum exists.
- ifsc-check: Validate an Indian IFSC by RBI structure (BBBB0NNNNNN; 5th character always 0).
- abn-check: Validate an Australian Business Number by its mod-89 checksum (11 digits).
- luhn-check: Validate any 12-19 digit number by the Luhn mod-10 algorithm (card-style checksums). Never submit real card numbers.
- isbn-check: Validate an ISBN-10 (mod-11) or ISBN-13 (1,3-weight mod-10) checksum.
- e164-check: Validate a phone number's E.164 structure (+CC, 8-15 digits, no leading zero).
- sedol-check: Validate a UK/Ireland security identifier by its (1,3,1,7,3,9)-weight mod-10 checksum.
- vendor-onboarding-pack: Screen a vendor's identifiers in ONE signed call: IBAN + LEI + VAT + UK company number — each checksummed, one verdict, one receipt. Half the price of four single checks.
- settlement-history-check: On-chain counterparty check: USDC transfers SENT and RECEIVED by an address over the last ~48h of Base blocks (counts, volumes, sample tx hashes). Preflighted so you never pay during an RPC outage.

Price from $0.000999–0.05 per call, DYNAMIC (idle prices decay toward the floor, demand bumps them up — watch GET /health for live quotes) USDC/call. Non-custodial; payer->seller direct on Base.

## Marketplace
- Listed on the x402 Registry: https://x402-registry.akrivis.workers.dev (crawl-verified, sha256-snapshotted)
- Buyer-side MCP payer (auto-handles the 402 dance): x402-payer