# DNS SRV Record Lookup for STUN over TCP

> DNS SRV Record Lookup for STUN over TCP is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.007/call, status unknown (last checked 2026-10-19).

Resolves SRV DNS records at _stun._tcp.{hostname} given a registrable domain name, returning STUN-over-TCP service location data.

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/dns-srv-stun-tcp?utm_source=zero.xyz
- Price: $0.007/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-19
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/dns-srv-record-lookup-for-stun-over-tcp-862a2464
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ERp7h0DDQbHB3NEZgIpwO

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-srv-record-lookup-for-stun-over-tcp-862a2464 -d '<json body>'
```

Example prompt: Look up the STUN-over-TCP SRV DNS records for example.com and tell me which server and port to use.

## When to prefer this

Use this endpoint when an agent needs to programmatically discover STUN-over-TCP service endpoints via DNS SRV records for a given domain, particularly in WebRTC, VoIP, or NAT traversal scenarios. Prefer the free sandbox POST /v1/sandbox/dns-srv-stun-tcp endpoint during development or testing. Choose this paid endpoint when the sandbox is unavailable or for production lookups.

## Known failure modes

- No SRV record exists for the given hostname — returns empty result or not-found error
- Invalid or malformed hostname input — returns validation error
- DNS resolution timeout or network failure — returns error
- Hostname exceeds 253-character limit — rejected by schema validation
- Payment not provided or insufficient — request rejected with 402 status

## How this service works

Call when an agent needs SRV records at _stun._tcp.{hostname} for STUN over TCP. The caller sends the registrable domain, not the underscored name. Exact $0.007 USDC. Prefer unpaid POST /v1/sandbox/dns-srv-stun-tcp first.

## Output

Returns the SRV record data found at _stun._tcp.{hostname}, including fields such as priority, weight, port number, and target hostname of the STUN server. If no record exists, returns an empty or error response.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "hostname": {
   "type": "string",
   "examples": [
    "example.com"
   ],
   "maxLength": 253,
   "minLength": 1,
   "description": "Public DNS hostname such as example.com. Not a URL, not an IP literal, and not a private name."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/dns-srv-record-lookup-for-stun-over-tcp-862a2464/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentshelf.syntexa.ch](https://www.zero.xyz/host/agentshelf.syntexa.ch/llms.txt)