People are handing routine purchases to their assistants — and every store on the internet still asks for an email and a card the assistant can't provide. Contra makes your existing API or shop checkout-ready for that moment: identity, a payment in dollars, policy, and a signed receipt on every call. No rebuild.
People are teaching their assistants to buy. Nobody is making the shops ready for that moment — because the entire commerce stack assumes a person is sitting at the keyboard.
An assistant can't fill a checkout form or own a Visa on the customer's behalf. Contra settles in dollars instead: instant, sub-cent, no chargebacks.
Signup, email verification, API-key application — every one is a human step. Contra's answer is HTTP 402: pay the price, get the goods. No account exists.
Who bought what, and what was delivered? Every Contra sale emits an Ed25519-signed receipt both sides can verify forever.
You paste the endpoint you already have and set a price in dollars. From there, every sale is four wire-level steps — the person just asked, their assistant did the rest.
Your shop gets a Contra URL. Your backend stays exactly as it is.
← 402 Payment RequiredThe challenge names the price in dollars. Settlement is instant and costs ~nothing.
💳 $1.50 · <1sThe assistant retries with cryptographic proof of payment. Contra verifies and proxies to you.
X-PAYMENT: …Signed record of buyer, price, policy, and a hash of what was delivered.
X-Contra-Receipt: 352d88…A Contra listing isn't a link you have to market — it becomes a native tool inside the assistants themselves.
Any Claude- or Cursor-class assistant plugs into every listing at once:
Any HTTP client can pay the challenge and retry — no SDK, no account:
A small take on every sale — viable at micropayment scale only because settlement fees are effectively zero. No card network can bill a ten-cent transaction.
from pasting your endpoint to your first listing — test it live before you publish
from 402 challenge to a settled payment in dollars
of sales carry a verifiable signed receipt — yours and the buyer's, forever
Have Claude? Scan the code — or tap Connect — to add Contra to it. No Claude? Open the web app and buy through Contra’s own assistant. Either way you get an account and can buy any listed tool, pay-per-call, in dollars.
merchant console → paste endpoint → price in dollars → publish. 402 does the rest.