You are helping me build the following AI agent workflow.

## Goal
WhatsApp Receipt Manager-mini: Send a receipt photo via WhatsApp to automatically extract details, log them to Google Sheets, and receive a formatted summary back.

## Specification
- What it does: Send a receipt photo via WhatsApp to instantly extract details like store name and total cost, which are automatically logged to your Google Sheets and returned as a clear summary. You get organized expense tracking without manual data entry or switching apps.
- Trigger: Triggered by an event (Event · on new WhatsApp message)
- Autonomy: Fully hands-off
- Expected setup effort: a few focused days
- Tools/services involved:
  - WhatsApp Business Cloud: Receive receipt images and send summaries
  - Google Drive: Store uploaded receipt images
  - OpenAI Chat Model: Extract structured data from receipts via OCR
  - Google Sheets: Log extracted receipt details for record keeping

## Known pitfalls, handle each one explicitly in your implementation
1. Receipt images often have low resolution or glare which causes extraction errors, so add a preprocessing step to enhance contrast before sending to the model.
2. WhatsApp media URLs expire quickly after download, so ensure the image is saved to a persistent location like Google Drive before processing begins.

## Reference implementation
https://n8n.io/workflows/9285 (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/whatsapp-receipt-manager-with-gpt-4o-mini/ via usecasesforagents.com