You are helping me build the following AI agent workflow.

## Goal
Voice Appointment Booking: A Vapi voice agent takes calls, checks your calendar for open slots with buffers, and books appointments directly.

## Specification
- What it does: You can book appointments hands-free by calling a Vapi voice assistant that captures your details and finds open time slots in Google Calendar. The agent checks for conflicts with buffers and either suggests available times or books the slot directly without needing human intervention.
- Trigger: Triggered by an event (Event · incoming voice call)
- Autonomy: Fully hands-off
- Expected setup effort: under an hour
- Tools/services involved:
  - Vapi AI: Voice agent handling calls and tool routing
  - Google Calendar: Checking availability and booking events
  - n8n Webhook: Receiving tool calls from Vapi
  - Code Node: Calculating potential time slots and filtering conflicts

## Known pitfalls, handle each one explicitly in your implementation
No documented pitfalls for this recipe. Apply your own review before going live.

## Reference implementation
https://n8n.io/workflows/8972 (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/automated-voice-appointment-booking/ via usecasesforagents.com