# reverse-dns-via-dnssb

> reverse-dns-via-dnssb is a paid API for AI agents from ip.intel.rallylive.ca, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-11).

Performs a reverse DNS (PTR) lookup for an IPv4 address using the DNS.SB resolver, returning hostnames, TTL, response code, and forward-confirmed reverse DNS (FCrDNS) status.

## Facts

- Endpoint: GET https://ip.intel.rallylive.ca/ip/ptr/via/dnssb?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/reverse-dns-via-dnssb-097328ae
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_-n9NRsKXOA5qMcMgv9kld

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 reverse-dns-via-dnssb-097328ae
```

Example prompt: What is the reverse DNS hostname for 8.8.8.8 according to DNS.SB, and does its PTR record forward-confirm back to the same IP?

## When to prefer this

Use this endpoint when you specifically want the DNS.SB resolver's perspective on a PTR record — useful for comparing resolver answers, detecting filtered or stale PTR entries, or validating forward-confirmed reverse DNS (FCrDNS) as part of email authentication checks or IP reputation analysis. Prefer this over generic reverse DNS tools when resolver-specific attribution matters.

## Known failure modes

- IP has no PTR record — DNS.SB returns NXDOMAIN response code
- PTR exists but forward A record does not point back — FCrDNS flag is false
- DNS.SB resolver timeout or unavailability — service may return an error or empty response
- Invalid IPv4 address input — may return a validation error
- PTR record exists but is stale — TTL may indicate cached data that differs from other resolvers

## How this service works

Reverse DNS (PTR) of an IPv4 address as answered by DNS.SB: the hostname(s), TTL and response code, plus whether the PTR's forward A record points back (forward-confirmed reverse DNS). Compare resolvers for stale or filtered answers. $0.01 per lookup.

## Output

Returns the PTR hostname(s) associated with the queried IPv4 address as answered by DNS.SB, along with the TTL (time-to-live), the DNS response code (e.g. NOERROR, NXDOMAIN), and a forward-confirmed reverse DNS (FCrDNS) flag indicating whether the PTR record's hostname resolves back to the original IP via an A record.

## 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",
     "properties": {}
    }
   },
   "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/reverse-dns-via-dnssb-097328ae/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from ip.intel.rallylive.ca](https://www.zero.xyz/host/ip.intel.rallylive.ca/llms.txt)