You are helping me build the following AI agent workflow.

## Goal
Simple SMS Messaging System: Manually trigger a workflow to send an SMS via Textbelt by providing a phone number, message body, and API key.

## Specification
- What it does: Send an SMS instantly by providing your phone number, message body, and API key to trigger a manual workflow that delivers the text via Textbelt and confirms whether it succeeded or failed.
- Trigger: Run manually (Manual · on demand)
- Autonomy: Fully hands-off
- Expected setup effort: under an hour
- Tools/services involved:
  - HTTP Request: Sending SMS via Textbelt API

## Known pitfalls, handle each one explicitly in your implementation
1. The API returns plain text responses rather than JSON which requires parsing logic to extract success status accurately.
2. Phone numbers must include country codes without leading zeros so add a formatting rule to ensure valid E.164 format.

## Reference implementation
https://n8n.io/workflows/6228 (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/simple-sms-messaging-system/ via usecasesforagents.com