Isip

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What it does

Point Claude Desktop, Cursor, or any MCP client at isip and your agent can dial a real phone number, speak (TTS), listen (STT), record the call, and report back a transcript — no Twilio app to build, no SaaS platform, no Docker required. It's built on the native, battle-tested PJSIP stack.

Under the hood there are three ways to drive a call:

1. MCP server — expose calling as tools to any AI agent.
2. Python SDK (Sippy) — a clean high-level API: sippy.call(target, prompt=…) → transcript.
3. CLI (siptester) — single calls or JSON-defined test suites.

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Your agent, making a phone call

Once the MCP server is connected to Claude Desktop or Cursor, the model can place calls in plain language:

You:    "Call +1 512-555-0142, introduce yourself, and ask whether they're open today."
Claude: 📞 Calling… connected (24.1s).
        Transcript: "Hi! Yes, we're open until 6pm today. How can I help?"

MCP tools exposed to the agent:

Tool	What it does
place_call(phone, prompt)	Dial a number, speak a prompt, transcribe the response
list_recordings()	Review prior call recordings + transcripts

The agent drives the phone; isip handles SIP signaling, audio, TTS/STT, and recording.

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Why this exists

Giving an agent a phone unlocks two things:

1. Testing voice AI — script and regression-test SIP voice agents, trunks, gateways, and IVRs from code or from an agent itself.
2. Agent-to-agent telephony (the bigger idea) — an AI that handles the hour-long hold calls humans hate (e.g. insurance verification of benefits), and negotiates AI-to-AI when the other side is automated too — turning a one-hour hold into seconds.

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Quick start

Prerequisites

• macOS (10.15+) · Python 3.12+ · Homebrew

Install

# 1. System dependencies
brew install pjproject ffmpeg

# 2. Clone + set up the SDK
git clone https://github.com/nwalker85/isip.git
cd isip/sdk/python
python3.12 -m venv .venv && source .venv/bin/activate
pip install -e .

# 3. Configure credentials
cp ../../.env.example ../../.env   # then edit with your keys

.env:

# AI services
OPENAI_API_KEY=sk-...
DEEPGRAM_API_KEY=...
ELEVENLABS_API_KEY=...        # optional

# SIP gateway
SIP_USERNAME=your_username
SIP_PASSWORD=your_password
SIP_GATEWAY=<your-gateway>.sip.livekit.cloud

Connect it to your agent (MCP)

cd mcp-server-isip
pip install -e .

Add to Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "isip": {
      "command": "mcp-server-isip",
      "cwd": "/path/to/isip"
    }
  }
}

Then just ask Claude to place a call. See mcp-server-isip/QUICKSTART.md for the full setup.

Or call from Python

from siptester import Sippy, VoiceService, SipHeaders

sippy = Sippy(
    voice_service=VoiceService("openai", "tts-1"),
    transcription_service=VoiceService("deepgram", "nova-2"),
)
target = SipHeaders(sip_to="sip:+15125550142@<your-gateway>.sip.livekit.cloud")
result = sippy.call(target, prompt="Hello, this is a test call.")

if result.established:
    print(result.duration, result.transcript)

One-liner:

from siptester import quick_call
print(quick_call(phone="+15125550142", prompt="Hello, is anyone there?",
                 username="user", password="pass").transcript)

Or from the CLI

source sdk/python/.venv/bin/activate

siptester call \
  --gateway "$SIP_GATEWAY" --user "$SIP_USERNAME" --password "$SIP_PASSWORD" \
  --phone +15125550142 --prompt-text "Hello, this is a test" \
  --openai-key "$OPENAI_API_KEY" --deepgram-key "$DEEPGRAM_API_KEY"

# Or a JSON test suite:
siptester suite --suite tests/example_tests.json \
  --gateway "$SIP_GATEWAY" --user "$SIP_USERNAME" --password "$SIP_PASSWORD"

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Architecture

  AI agent (Claude / Cursor)
        │  MCP
        ▼
  mcp-server-isip ──► Sippy (high-level API) ──► SipTestClient ──► PJSIP (native)
                              │                                        │
                       OpenAI TTS / Deepgram STT                 SIP gateway (e.g. LiveKit)
                                                                       │
                                                                  the phone network

• MCP server (mcp-server-isip/) — agent-facing tools.
• Python SDK (sdk/python/siptester/) — Sippy high-level API, low-level SipTestClient, and the siptester CLI.
• PJSIP — native SIP signaling.
• AI services — OpenAI TTS for prompts, Deepgram STT for transcription; ElevenLabs optional.

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Status

A working prototype, verified end-to-end (live calls against a LiveKit SIP gateway):

Component	Status
PJSIP bindings	✅ working
Python SDK / Sippy	✅ working
OpenAI TTS · Deepgram STT	✅ working
Live SIP call (LiveKit gateway)	✅ ~28s call, transcript received
Audio recording	✅ working
MCP server	✅ AI agent can place calls
CLI	✅ working

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Roadmap

• SDK hardening — packaging, unit tests with PJSIP mocking, type coverage.
• CLI — config file (~/.isip/config.yaml), JSON output, parallel runs with retries.
• Agent telephony — richer MCP tools (multi-turn conversations, DTMF/IVR navigation, call transfer), and the agent-to-agent VOB use case.
• Cross-platform — Linux validation, Docker image optimization.

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Troubleshooting

• pjsua/PJSIP not found → brew install pjproject
• ffmpeg not found → brew install ffmpeg
• Microphone permissions → System Settings → Privacy & Security → Microphone
• NAT/firewall → set local_ip to your public IP on SipHeaders(...)
• SIP auth failed → verify credentials with your SIP provider; email-style usernames are normalized automatically.

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Credits & license

Built with PJSIP, OpenAI (TTS), Deepgram (STT), and tested against the LiveKit SIP gateway.

MIT — see LICENSE.