COMMERCE ON
A BASIC PHONE.

No data connection, no app, no storage, no smartphone. It works on a handset that costs very little and is already in the hand of the participant GRAJ most wants to reach.

Sessions are short, menus shallow, input numeric. That forces a flow down to what a transaction genuinely needs, which turns out to be a good discipline for every other interface too.

Anybody who has used mobile money already knows the interaction. Meeting people inside a pattern they use daily beats teaching them a better one.

This page used to say "not built, and the blocker is commercial rather than technical". That was half right, and the half it got wrong is the half worth building. An aggregator supplies the TRANSPORT — it answers the short code and posts the dialed path to a webhook, expecting a menu back or a hang-up. That webhook and the menu behind it are ours, and both exist now: the menu engine is a pure function of what you have typed, every screen is measured against the 182 bytes a USSD screen actually holds, a choice that did not fit on the screen cannot be selected by typing its number, and an order is placed only on an explicit confirm — never on the quantity you typed, because a mistyped digit is the difference between four cases and four hundred. Orders go through the same writer as a browser order, so the cheapest phone is priced, taxed and settled exactly like the most expensive one.

The menu is more than "place an order": order from a brand (with how many are in stock, when the brand counts its stock), see your last order, reorder your last order in two key presses at today's price, hear what you owe — per currency, what is overdue and the oldest due date, the same figures as your statement of account — and see your three most recent orders. The same menu answers a text or a WhatsApp message to a seller's own number. Confirming you paid by mobile money is not on it yet: a payment reference typed on a keypad is a claim on somebody else's money, so it is recorded only by the seller who received it.

The gateway refuses every request until a shared secret is configured for a contracted aggregator — including well-formed ones. The caller supplies the phone number and the phone number identifies the buyer, which is simply how USSD works; it also means an open endpoint waiting for a contract would let anyone order as anybody whose number they knew. A wrong secret is answered exactly like a missing one, and a number that is on GRAJ exactly like one that is not, so nothing can be learned by guessing. What remains is a contract per market, which is a commercial arrangement rather than a code change.