What it does
PayFox turns any Facebook Page into an AI-powered store inside Messenger. Customers send a voice note, browse a product catalog, tap "Buy", and pay with PayPal — all in the same chat. Payments confirm automatically via webhooks.
One voice note → product cards → one tap → paid → receipt. Automatically.
Inspiration
Over 500 million people use Facebook Messenger every month. Millions of small businesses — especially in Southeast Asia — sell through chat. But taking payment means sending bank account numbers, waiting for transfer screenshots, and manual reconciliation. That's friction, fraud risk, and lost sales.
We asked: what if the entire store — catalog, checkout, payment, receipt — lived inside one chat?
How we built it
The flow (end-to-end, working live):
- Discover — new customer opens the chat → automatic welcome message
- Browse — voice note or type "catalog" → product cards with photos, prices, and Buy buttons (Messenger Generic Template)
- Buy — tap Buy Now → PayFox creates a PayPal order (Orders API v2) and sends the payment link
- Pay — customer pays on PayPal (card, bank, or balance)
- Auto-capture — PayPal webhook CHECKOUT.ORDER.APPROVED → PayFox auto-captures the payment → money moves
- Receipt — PayPal webhook PAYMENT.CAPTURE.COMPLETED → PayFox sends a receipt card (Messenger Receipt Template) with the customer's name, product photo, order number, and total — automatically in chat
PayPal APIs used:
- Orders API v2 — create order, approve link, auto-capture on approval
- OAuth2 — client credentials token management
- Webhooks — live-registered; APPROVED triggers capture, COMPLETED triggers the receipt card
- Invoicing v2 — paypal_invoice tool for formal B2B orders
AI brain:
- Muse Spark 1.3 (Meta Model API) — routes intents, calls tools, transcribes voice notes, writes every reply. Zero hardcoded responses — even the quick "On it!" acknowledgment is model-generated via a parallel intent-router request.
Store management:
- Store owners manage the catalog conversationally: "add product: Gayo Coffee 1kg, $35" → the catalog updates instantly
- Product photos generated with Muse Image
- Product cards served via Messenger Generic Templates
- Order tracking (order_id → Messenger user) persists to disk — webhooks survive restarts
Challenges we faced
The tool-routing fix. Early versions confused "show catalog" with "add product" — the model picked the wrong tool 100% of the time with real users. Fix: tool descriptions with explicit routing rules + a system prompt that maps intent → tool name. Result: 100% correct routing in E2E tests.
The catalog singleton bug. Two catalog instances (one for the agent, one for the webhook handler) meant every Buy button tap returned "product not found" — the agent added products to one catalog, the BUY button read from a stale second one. Fix: one shared catalog instance across the entire process.
The auto-capture lesson. PayPal Orders API is two-step: customer approves, then the merchant captures. Without the capture call, money stays in limbo even after the customer pays. PayFox auto-captures on the APPROVED webhook — money moves without human intervention.
Dev-mode Messenger. The demo runs in development mode (standard pre-launch). Production rollout requires Meta's app review. The harness is production-ready beyond that gate.
What we learned
- Conversational commerce needs precise tool routing — "similar" tool descriptions confuse LLMs. Explicit routing rules in system prompts are the fix.
- PayPal webhooks are the backbone of automated commerce — they turn a "payment sent" into "order confirmed, receipt delivered, customer informed" without any human in the loop.
- The difference between a tech demo and a product is the confirmation loop: welcome → browse → buy → pay → automatic receipt. If the customer doesn't get instant proof of payment, trust breaks. ## What it does
How we built it
Challenges we ran into
Accomplishments that we're proud of
What we learned
What's next for PayFox — AI Commerce Agent
Built With
- agentic-commerce
- facebook-messenger
- go
- meta-model-api
- muse-spark
- paypal
- paypal-orders-api
- paypal-webhooks
- voice-notes
