You are helping me build the following AI agent workflow.

## Goal
Coach Training with SMS: Onboards new coaches via webhook and delivers daily 9 AM training SMS with keyword auto-replies and progress tracking in Google Sheets.

## Specification
- What it does: Get your new coaches onboarded instantly via webhook while receiving their first daily training message at 9 AM. You can track their entire 30-day progress in Google Sheets and handle all incoming questions with automatic keyword replies.
- Trigger: Triggered by an event (Event · on new coach registration)
- Autonomy: Fully hands-off
- Expected setup effort: about an afternoon
- Tools/services involved:
  - n8n: Workflow orchestration and automation logic
  - Twilio: Sending daily training SMS messages
  - Google Sheets: Storing coach data and training content

## Known pitfalls, handle each one explicitly in your implementation
1. Google Sheets API quotas are strict per minute, so batch updates if onboarding multiple coaches at once.
2. SMS character counts exceed 160 chars easily, so implement message splitting or link shortening carefully.
3. Webhook security is vital, add a secret header validation step to prevent unauthorized trigger submissions.

## Reference implementation
https://n8n.io/workflows/8723 (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/automate-coach-training-with-sms/ via usecasesforagents.com