# Reverse Dns Lookup — MCP tool `findutils:reverse_dns_lookup`

Look up the reverse DNS (PTR) hostname of an IPv4 or IPv6 address through a public DNS-over-HTTPS resolver. Returns the in-addr.arpa or ip6.arpa name queried, the response code and every PTR hostname with its TTL; found is false when there is no PTR record (NXDOMAIN or an empty answer).

- Category: network
- MCP server: https://mcp.findutils.com/ (Streamable HTTP, API key for tools/call, 120 req/min per IP)
- REST endpoint: POST https://api.findutils.com/api/tools/reverse-dns-lookup/execute (API key, 60 req/min per IP)
- API key: Running a tool needs an API key. Keys are not for sale yet: ask for early access. Without a key, a tool call answers HTTP 402 Payment Required with the error code PAYMENT_REQUIRED. The catalog and the schemas stay open without a key. https://findutils.com/api/#api-keys
- Network tool: fetches a fixed, hard-coded public upstream (never a private host).
- Reference page: https://findutils.com/mcp/reverse-dns-lookup/
- Same tool on the other surface: https://findutils.com/api/reverse-dns-lookup/

## Connect

```bash
claude mcp add findutils --transport http https://mcp.findutils.com/ --header "Authorization: Bearer YOUR_API_KEY"
```

Claude Desktop (`claude_desktop_config.json`):

```json
{
  "mcpServers": {
    "findutils": {
      "url": "https://mcp.findutils.com/",
      "headers": {
        "Authorization": "Bearer YOUR_API_KEY"
      }
    }
  }
}
```

## Call the tool (verified example)

```bash
curl -X POST https://mcp.findutils.com/ \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/call",
    "params": {
      "name": "reverse_dns_lookup",
      "arguments": {
        "ip": "8.8.8.8"
      }
    }
  }'
```

## Input schema

| Argument | Type | Required | Description |
|---|---|---|---|
| `ip` | string | yes | IPv4 or IPv6 address, e.g. "8.8.8.8" or "2001:4860:4860::8888". |
| `resolver` | string (google \| cloudflare) | no | Public resolver to ask: google (dns.google) or cloudflare (cloudflare-dns.com). Default: `"google"`. |

Example arguments (verified):

```json
{
  "ip": "8.8.8.8"
}
```

## Also a REST endpoint

```bash
curl -X POST https://api.findutils.com/api/tools/reverse-dns-lookup/execute \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "ip": "8.8.8.8"
  }'

# Parameter schema (no key needed)
curl https://api.findutils.com/api/tools/reverse-dns-lookup
```

Full REST reference: https://findutils.com/api/reverse-dns-lookup/ · OpenAPI 3.1 spec: https://findutils.com/api/openapi.json

---
Full catalog: POST https://mcp.findutils.com/ with method `tools/list` · https://findutils.com/mcp/ · https://findutils.com/llms.txt