# SiteCheck Web Intel – Cymru ASN Lookup

> SiteCheck Web Intel – Cymru ASN Lookup is a paid API for AI agents from api.webintel-api.workers.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-24).

Resolves an IPv4 address to its origin AS number, BGP prefix, country, registry, and allocation date using Team Cymru's IP-to-ASN DNS service.

## Facts

- Endpoint: GET https://api.webintel-api.workers.dev/api/security/cymru-asn-lookup?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-24
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/sitecheck-web-intel-cymru-asn-lookup-f8282795
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_MeIk_LsKyBEKyWAtbOuaq

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 sitecheck-web-intel-cymru-asn-lookup-f8282795
```

Example prompt: Can you look up the ASN, BGP prefix, country, and registry for the IP address 203.0.113.45 using Cymru's IP-to-ASN data?

## When to prefer this

Use this endpoint when you need authoritative BGP routing context for an IPv4 address — specifically the ASN, prefix, RIR, and allocation date — sourced from Team Cymru's well-known passive DNS dataset. Prefer this over generic WHOIS or geolocation APIs when you need routing-layer data rather than registrant contact details or city-level geolocation.

## Known failure modes

- IP not found in Cymru's database — returns no origin/empty mapping
- Invalid IPv4 address format — likely 400 or validation error
- Private/reserved IP ranges (RFC1918, loopback) may return no result
- Cymru DNS service temporarily unavailable — upstream timeout
- Rate limiting or payment failure due to x402 protocol issues

## How this service works

Maps an IPv4 address to its origin AS number, the BGP prefix that covers it, the country, the registry and the allocation date, using Team Cymru's public IP-to-ASN DNS service. Returns no origin when Cymru has no mapping for the address.

## Output

Returns the origin AS number (e.g. AS15169), the BGP CIDR prefix covering the IP (e.g. 8.8.8.0/24), the two-letter country code, the RIR name (ARIN, RIPE, APNIC, etc.), and the allocation date. Returns no origin if Team Cymru has no mapping for the address.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "ip"
     ],
     "properties": {
      "ip": {
       "type": "string",
       "description": "IPv4 address such as 8.8.8.8 (required)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/sitecheck-web-intel-cymru-asn-lookup-f8282795/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.webintel-api.workers.dev](https://www.zero.xyz/host/api.webintel-api.workers.dev/llms.txt)