You are helping me build the following AI agent workflow.

## Goal
WhatsApp Expense Tracker Reports: Send natural language messages to WhatsApp to log expenses or generate financial reports, with data stored in PostgreSQL.

## Specification
- What it does: Log expenses instantly by sending natural language messages to WhatsApp, where the tool automatically categorizes your spending and saves it securely. You receive immediate summaries and daily financial reports directly in your chat without needing to open an app or spreadsheet.
- Trigger: Triggered by an event (Manual · on WhatsApp message or Scheduled · daily)
- Autonomy: Fully hands-off
- Expected setup effort: about an afternoon
- Tools/services involved:
  - WhatsApp Business Cloud: Receive and send messages
  - OpenRouter Chat Model: Parse natural language into structured data
  - Postgres: Store financial transaction records

## Known pitfalls, handle each one explicitly in your implementation
1. WhatsApp messages often contain emojis and informal slang so you must preprocess text to remove non-numeric characters before parsing amounts.
2. Currency symbols vary by region so ensure your LLM prompt explicitly handles different formats like $10, 10€, or ten dollars as valid numeric values.
3. Storing raw chat logs can lead to data privacy issues so you should anonymize user identifiers and encrypt sensitive financial data in the database.

## Reference implementation
https://n8n.io/workflows/4136 (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-expense-tracker-with-ai-reports/ via usecasesforagents.com