# DNS Reverse PTR Lookup

> DNS Reverse PTR Lookup is a paid API for AI agents from dns.openverbs.com, paid per call via x402, $0.006/call, status unknown (last checked 2026-09-15).

Resolves an IPv4 or IPv6 address to its PTR hostname(s) via reverse DNS lookup

## Facts

- Endpoint: POST https://dns.openverbs.com/v1/reverse
- Price: $0.006/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/dns-reverse-ptr-lookup-29adf7cb
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_O9FluIa12i7_-5oExfM93

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 dns-reverse-ptr-lookup-29adf7cb -d '<json body>'
```

Example prompt: What's the reverse DNS hostname for the IP address 8.8.8.8? Do a PTR record lookup and tell me what hostname it resolves to.

## When to prefer this

Use this endpoint when you need to reverse-resolve an IP address to its PTR hostname via standard DNS — for tasks like mail server verification, security log enrichment, infrastructure auditing, or confirming that reverse DNS is correctly configured. Prefer this over forward DNS lookup (A/AAAA) when you have an IP and need the associated hostname. Not suitable for ENS/blockchain name resolution or WHOIS lookups.

## Known failure modes

- Invalid or malformed IP address returns an error
- No PTR record configured for IP returns an empty list
- Network timeout or upstream DNS resolver failure
- IPv6 address formatting issues (e.g. non-canonical form)
- Rate limiting or payment failure via x402 protocol

## How this service works

Reverse-resolve an IPv4 or IPv6 address to its PTR hostname(s). No PTR record returns an empty list. This is reverse DNS (PTR) — not ENS or onchain name resolution.

## Output

A list of PTR hostnames associated with the given IP address. If no PTR record exists, an empty list is returned. For most IPs this is a single hostname (e.g. 'one.one.one.one'), but multiple entries are possible.

## 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",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "required": [
      "ip"
     ],
     "properties": {
      "ip": {
       "type": "string",
       "description": "IPv4 or IPv6 address, e.g. \"1.1.1.1\"."
      }
     },
     "additionalProperties": false
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/dns-reverse-ptr-lookup-29adf7cb/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from dns.openverbs.com](https://www.zero.xyz/host/dns.openverbs.com/llms.txt)