AI agent, 2026
Multilingual WhatsApp Commerce Agent
A WhatsApp agent that answers shop customers in English, Sinhala, Tamil and Singlish, and can only quote what the product catalogue says.
Four registers, one agent
The model can only quote what catalogue.search returns. If nothing comes back, it says so instead of guessing.
- Languages: English, Sinhala, Tamil and Singlish
- 4
- Message per turn, by policy
- 1
- Model, chosen for speed and cost per conversation
- Haiku 4.5
The problem
In Sri Lanka a lot of retail happens on WhatsApp. A customer sends a photo of a school book list or asks whether a bag comes in blue, and the sale goes to whoever answers first. For a small shop, answering first means someone watching a phone all day, and answering in whatever the customer wrote: English, Sinhala, Tamil, or Singlish, the romanised Sinhala many people type on their phones.
Pehesara Book Shop had exactly this problem. Messages arrived faster than anyone could reply, in four languages, and the unanswered ones were lost sales.
The constraint
An AI that answers quickly but invents a price, or promises stock the shop does not have, is worse than no AI at all. The shop would spend the afternoon apologising. So the brief was never “a chatbot”. It was a salesperson who cannot lie about the shelf.
Cost mattered too. WhatsApp business messaging is paid, and a bot that replies in three messages where one would do triples the bill.
The decision
- Tool-enforced grounding. The model does not know the catalogue. It has to call a catalogue tool, and it may only quote what that tool returns: names, prices and availability. If the tool returns nothing, the answer is “let me check”, never a guess.
- Reply in the customer’s language. Sinhala gets Sinhala, Tamil gets Tamil and Singlish gets Singlish. Nobody has to switch to English to buy a pencil.
- One message per turn. Every customer message gets exactly one reply. It reads more like a person, and it keeps the cost of a conversation predictable.
- A small, fast model. Claude Haiku 4.5 is quick enough to feel instant on WhatsApp and cheap enough for a shop’s margins.
The outcome
The agent is live for Pehesara Book Shop. Because the grounding lives in the tool contract rather than the prompt, the same agent can be pointed at a different shop’s catalogue. That is what CEYLAI is doing now: packaging it for other businesses, timed to roll out ahead of Meta’s October 2026 pricing change.