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