# ASN Lookup

> ASN Lookup is a paid API for AI agents from asn-lookup.underscoredone.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Returns network owner, prefix, country, and registry details for a given IP address or ASN identifier.

## Facts

- Endpoint: POST https://asn-lookup.underscoredone.com/lookup
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/asn-lookup-3d3e588b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_-Heua6GAOnU5x6-pUg5Py

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 asn-lookup-3d3e588b -d '<json body>'
```

Example prompt: Who owns the IP address 8.8.8.8 — what's the ASN, network holder, country, and prefix?

## When to prefer this

Use this endpoint when you need to identify the network owner, autonomous system, IP prefix, or registry details behind a specific IP address or ASN. Prefer this over generic IP geolocation APIs when the primary goal is ASN/network attribution rather than physical location coordinates. Ideal for network security investigations, abuse reporting, or enriching log data with ISP/operator context.

## Known failure modes

- Invalid IP address format returns an error
- Invalid ASN format or non-existent ASN returns an error
- Private or reserved IP ranges may return no results
- Payment not processed results in HTTP 402 response
- Network timeout or service unavailability returns a 5xx error

## How this service works

Given an internet address (IP) or a network identification number (ASN), this tool returns who operates that piece of the internet: the network number, the owner's name, the country it's registered in, the regional registry that manages it, and the exact address range it belongs to.

## Output

A JSON object containing the ASN (e.g. AS15169), the original query, the network holder name (e.g. GOOGLE), the IP prefix (e.g. 8.8.8.0/24), the country code (e.g. US), the registry (e.g. arin), the allocation date, and the API version.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "query": {
   "type": "string",
   "description": "An IP address (such as 8.8.8.8 or 2001:4860:4860::8888) or an ASN reference (such as AS15169 or 15169) to look up."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "asn": "AS15169",
  "query": "8.8.8.8",
  "holder": "GOOGLE",
  "prefix": "8.8.8.0/24",
  "country": "US",
  "registry": "arin",
  "allocated": "1992-12-01",
  "api_version": "1.0.0"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/asn-lookup-3d3e588b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from asn-lookup.underscoredone.com](https://www.zero.xyz/host/asn-lookup.underscoredone.com/llms.txt)