# SIP-over-TCP SRV DNS Lookup (agentshelf.syntexa.ch)

> SIP-over-TCP SRV DNS Lookup (agentshelf.syntexa.ch) is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-19).

Resolves SRV records at _sip._tcp.{hostname} for SIP over TCP, given a registrable domain name

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/dns-srv-sip?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-19
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/sip-over-tcp-srv-dns-lookup-agentshelf-syntexa-ch-3d75a0a5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_A4A9ep8iqsafvjfp-ReB-

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 sip-over-tcp-srv-dns-lookup-agentshelf-syntexa-ch-3d75a0a5 -d '<json body>'
```

Example prompt: Can you look up the SIP over TCP SRV records for the domain example.com so I can find the SIP server's host and port?

## When to prefer this

Use this endpoint when an agent needs to programmatically discover the SIP-over-TCP server location for a given domain via DNS SRV lookup, without having to run DNS tools locally. Prefer the free sandbox endpoint (/v1/sandbox/dns-srv-sip) first; fall back to this paid endpoint when the sandbox is unavailable or rate-limited.

## Known failure modes

- Domain has no _sip._tcp SRV record — returns empty or NXDOMAIN result
- Invalid or malformed hostname input
- Network timeout resolving DNS
- Domain does not exist — NXDOMAIN
- Payment not received — x402 payment required error

## How this service works

Call when an agent needs SRV records at _sip._tcp.{hostname} for SIP over TCP. The caller sends the registrable domain, not the underscored name. Exact $0.003 USDC. Prefer unpaid POST /v1/sandbox/dns-srv-sip first.

## Output

Returns the SRV record data for _sip._tcp.{hostname}, typically including priority, weight, port, and target hostname of the SIP server for TCP transport.

## 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/sip-over-tcp-srv-dns-lookup-agentshelf-syntexa-ch-3d75a0a5/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)