You are helping me build the following AI agent workflow.

## Goal
Multimodal WhatsApp AI Assistant: An AI assistant on WhatsApp that understands text, voice notes, images, and PDFs, remembering your last 10 messages to reply contextually.

## Specification
- What it does: Receive instant replies on WhatsApp that understand your text, voice notes, images, and PDFs by analyzing each format with specialized tools. The assistant remembers your last 10 messages to provide context-aware answers and can even send you audio responses for a seamless conversation.
- Trigger: Triggered by an event (Event · on incoming WhatsApp message)
- Autonomy: Fully hands-off
- Expected setup effort: about an afternoon
- Tools/services involved:
  - WhatsApp Business Cloud: Message trigger and delivery
  - OpenAI Chat Model: Text processing and response generation
  - OpenAI: Audio transcription, image analysis, and text-to-speech
  - Simple Memory: Maintaining conversation context

## Known pitfalls, handle each one explicitly in your implementation
1. Voice notes require transcription before analysis which adds latency so you should consider async processing for better user experience.
2. Large PDF files may exceed token or size limits in the OpenAI API so you need to add logic to truncate or summarize content first.
3. Audio responses must be encoded correctly as MP3 or OGG with proper headers otherwise the WhatsApp client will not play them.

## Reference implementation
https://n8n.io/workflows/3586 (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/multimodal-whatsapp-ai-assistant/ via usecasesforagents.com