SignalWire AI Agent (SWML)
Telephony platform with a built-in AI agent runtime defined declaratively in SWML: one per-minute rate covers realtime STT, the LLM and standard TTS, plus SWAIG function calling to your webhooks.
Overview
Best for: Phone agents where one predictable bundled rate including the LLM is preferred.
At a glance
$0.16/min includes STT, LLM and standard TTS; voice transport and premium voices extra. Bundled LLM not named.
Phone/SIP/WebRTC
Standard TTS included; ElevenLabs/premium TTS extra
Configurable via ai.languages or ai.multilingual.
No verified number.
Not verified.
Not verified in this research.
Features
- telephony
- function calling (SWAIG)
- post-call summary webhook (post_prompt_url)
- barge-in
- memory
- retrieval
- pronunciation hints
Pricing
| What | Price | Unit |
|---|---|---|
| AI Agent Runtime | $0.16 | per minute |
| Local inbound / outbound | $0.0066 / $0.008 | per minute |
| Local number | $0.50 | per month |
| ElevenLabs TTS | $0.000297 | per character |
SignalWire's own all-in estimate for standard SIP/PSTN usage with standard TTS. Premium/ElevenLabs voices add more.
Free tier: Not stated on pricing page.
Source: signalwire.com
Setup
- Create a SignalWire space and buy a number.
- Create a SWML script (dashboard or hosted URL) with answer + ai.
- Point the number's call handler at the SWML; add SWAIG functions that call your webhooks; set post_prompt_url for call summaries.
Endpoint
SWML served from your URL or the dashboardAuthentication
Project ID + API token
Quick start javascript
// Serve a minimal SWML AI agent (JSON form of SWML) from Express
import express from "express";
const app = express();
app.all("/swml", (req, res) => res.json({
version: "1.0.0",
sections: {
main: [
{ answer: {} },
{ ai: {
prompt: { text: "You are a customer service agent for Acme. Say you are an AI. Be brief." },
post_prompt: { text: "Summarize the call and any actions taken." },
post_prompt_url: "https://example.com/post-prompt-hook"
} }
]
}
}));
app.listen(3000);Written from the current docs. Check the vendor's SDK version before you ship.
Warnings
Premium voices cost extra
Standard TTS is included; ElevenLabs is billed per character and the page is inconsistent about how it applies to agents. Price your exact voice.
Higher headline than DIY
$0.16/min bundled is roughly 2x a DIY Twilio/Plivo + cheap model stack, but includes the LLM.
SWML learning curve
Agent behaviour lives in SWML/SWAIG rather than code, which is fast to start but different from Python/JS frameworks.
LLM choice
The bundled LLM is chosen by SignalWire; confirm which models and whether you can bring your own.
Plus 12 warnings that apply to all platforms and telephony APIs. See category warnings.
Limits
- Not published in sources reviewed
Models and products
| Name | Status |
|---|---|
| AI Agent Runtime | GA |
Docs and sources
Docs
Sources used
Which LLM is bundled; free trial; compliance.