You are helping me build the following AI agent workflow.

## Goal
Voice Appointment Booking Agent: Handles inbound calls to book appointments by checking Cal.com availability via ElevenLabs and confirming slots verbally.

## Specification
- What it does: You get appointments booked instantly through natural voice conversations without lifting a finger. The agent listens to your preferences, checks real-time availability via Cal.com, and confirms your slot verbally using ElevenLabs. If your first choice is unavailable, it negotiates alternative times until the booking is secured or you end the call.
- Trigger: Triggered by an event (Event · on inbound voice call)
- Autonomy: Fully hands-off
- Expected setup effort: a few focused days
- Tools/services involved:
  - ElevenLabs: Voice interaction and speech generation
  - Cal.com: Checking availability and booking meetings
  - HTTP Request: Connecting to n8n webhooks for tool execution

## Known pitfalls, handle each one explicitly in your implementation
1. Latency in voice processing can cause awkward pauses, so optimize the n8n workflow to minimize HTTP request delays.
2. Timezone mismatches between the caller and your calendar will lead to double bookings, so explicitly normalize all times to UTC before checking Cal.com.
3. ElevenLabs may misinterpret background noise as speech commands, add a silence detection threshold to prevent false triggers.

## Reference implementation
https://n8n.io/workflows/5670 (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/voice-appointment-booking-agent/ via usecasesforagents.com