# code402 ISIN Validator

> code402 ISIN Validator is a paid API for AI agents from hcrb.in, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-11).

Validates an ISIN (International Securities Identification Number) using offline deterministic checksum verification, returning validity, reason, country, and normalized form.

## Facts

- Endpoint: POST https://hcrb.in/v1/tools/isin-check/call?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/code402-isin-validator-d9efaa2f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_n0uD2uMzAUxSO4QpE976f

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability code402-isin-validator-d9efaa2f -d '<json body>'
```

Example prompt: Can you check whether the ISIN US0378331005 is valid — specifically confirm the checksum passes and tell me which country it belongs to?

## When to prefer this

Choose this endpoint when you need fast, offline, deterministic ISIN validation with checksum verification — no network scraping, no ML, no registry lookup required. Ideal for compliance pipelines, pre-trade checks, and data ingestion workflows where you need a cryptographically-accountable signed receipt per call and pay-per-use micro-pricing ($0.005 USDC). First 3 calls/day are free.

## Known failure modes

- Malformed or missing ISIN input returns valid=false with a descriptive reason
- ISIN with wrong length or non-alphanumeric characters fails format check before checksum
- Payment failure via x402 returns HTTP 402 before any validation is attempted
- Ambiguous or unsupported prefix may return scope as format-only rather than checksum-verifiable

## How this service works

Offline deterministic checks (no ML, no scraping) for business identifiers and rental due-diligence, paid per call via x402 (gasless EIP-3009 USDC on Base). Checksum-verifiable (IBAN, LEI, VAT, ABA, ISBN, SEDOL…) vs format-only (EIN, IFSC, SWIFT/BIC…) — every response returns a scope field. Non-custodial, signed receipts. First 3 calls/day free.

## Output

Returns a JSON object with: `valid` (boolean indicating whether the ISIN passes checksum), `reason` (human-readable explanation of why valid or not), `scope` (indicating checksum-verifiable vs format-only), `country` (ISO country code extracted from the ISIN prefix), and `normalized` (canonical form of the identifier). All checks are performed offline with no ML or external lookups.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "isin"
   ],
   "properties": {
    "isin": {
     "type": "string",
     "description": "12-character ISIN: 2-letter country code + 9 alphanumerics + check digit; spaces allowed."
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "schema": {
  "type": "object",
  "required": [
   "valid",
   "reason"
  ],
  "properties": {
   "tool": {
    "type": "string"
   },
   "scope": {
    "type": "string"
   },
   "valid": {
    "type": "boolean"
   },
   "reason": {
    "type": "string"
   },
   "country": {
    "type": "string"
   },
   "normalized": {
    "type": "string"
   }
  }
 },
 "example": {
  "valid": true,
  "reason": "checksum valid"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/code402-isin-validator-d9efaa2f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from hcrb.in](https://www.zero.xyz/host/hcrb.in/llms.txt)