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Voice & Phone Medium to set up Automation Voice/Phone Agent

Plivo and UltraVox AI Voice Assistant

Source reviewed Updated 2026-07-07

When Plivo receives a call, this workflow generates an XML response to join an UltraVox audio stream for AI voice assistant interaction.

What it does

You receive incoming calls from Plivo that automatically connect you to an AI voice assistant via UltraVox through a generated audio stream session. By configuring your API keys and system prompts, this workflow ensures every call triggers the correct interaction without manual setup.

Step by step

  1. Configure the Plivo application with an answer URL that points to your HTTP Request node.
  2. Set up the HTTP Request node to forward the incoming call payload to UltraVox's session creation endpoint.
  3. Store API keys for both Plivo and UltraVox in environment variables or secure configuration management.

Where the LLM does the work

  • Draft system prompts that define the voice assistant's persona, tone, and specific task objectives.
  • Design error handling logic to gracefully manage failed session connections or invalid payloads.
  • Optimize the XML response structure to ensure seamless audio stream initiation with UltraVox.

Watch out for

Plivo requires a publicly accessible HTTPS endpoint for callbacks so you must configure your firewall or tunneling tool correctly.
XML syntax errors will cause Plivo to drop the call so validate your response structure before deploying.

Tools that fit

Plivo Service Voice call initiation and XML response
UltraVox LLM AI voice assistant session management
HTTP Request API Connecting Plivo to UltraVox via API

The agent brief

Everything your agent needs, including the gotchas. Copy it and go.
agent-brief.md
You are helping me build the following AI agent workflow.

## Goal
Plivo and UltraVox AI Voice Assistant: When Plivo receives a call, this workflow generates an XML response to join an UltraVox audio stream for AI voice assistant interaction.

## Specification
- What it does: You receive incoming calls from Plivo that automatically connect you to an AI voice assistant via UltraVox through a generated audio stream session. By configuring your API keys and system prompts, this workflow ensures every call triggers the correct interaction without manual setup.
- Trigger: Triggered by an event (Event · on incoming call)
- Autonomy: Fully hands-off
- Expected setup effort: about an afternoon
- Tools/services involved:
  - Plivo: Voice call initiation and XML response
  - UltraVox: AI voice assistant session management
  - HTTP Request: Connecting Plivo to UltraVox via API

## Known pitfalls, handle each one explicitly in your implementation
1. Plivo requires a publicly accessible HTTPS endpoint for callbacks so you must configure your firewall or tunneling tool correctly.
2. XML syntax errors will cause Plivo to drop the call so validate your response structure before deploying.

## Reference implementation
https://n8n.io/workflows/3392 (workflow template)
Fetch and inspect this before building. If it matches my stack, adapt it;
if not, rebuild the pattern with my tools.

## Process requirements
1. Before building: ask me which of the listed tools I actually use and
   what my platform is (n8n / Make / code / other). Do not assume.
2. Adapt the pattern to my answers; do not force the reference stack.
3. Address every pitfall above; tell me how you handled each.
4. Provide a test plan I can run before letting this touch real data.
5. Ask before any step that sends messages, modifies data, or spends money.

Source: https://usecasesforagents.com/use-case/plivo-and-ultravox-ai-voice-assistant/ via usecasesforagents.com

Frequently asked questions

Can I use a different Voice & Telephony than Plivo?

Yes. Plivo is only the example voice & telephony in this recipe. The same flow works with Aloware, ElevenLabs, GoToWebinar and Twilio. Swap the voice & telephony connection and keep the rest of the setup as written.

Want this running in your business?

This is what I do. I design and build AI agents like this one, and keep them running. If you want it set up for your team instead of doing it yourself, get in touch.
Get in touch →

Who it's for

Built for developers who want the busywork around code automated, not the code itself.

Seen in the wild

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