Inspiration

In September 2026 a seller said an AI agent gave a stranger his address and agreed to a lowball price; the buyer turned up at 9:15 pm while he was out (The Next Web, 28 Sep 2026; the company disputes parts of the account). Agents can already sell for us. Nobody has made the handoff safe: who gets your address, when the money moves, and what proves the item left.

What it does

Stoop: sell anything without meeting anyone. Money moves only when your camera sees the item go.

Sell by voice with Alexa, or from the web. One photo and Amazon Bedrock prices it.
You set a lowest price the AI never sees. Every sale needs your yes.
The buyer pays, but the money is only held.
The address appears only inside their pickup window, on their phone.
An old phone or a Ring doorbell is the porch camera. A person at the door, then the item gone, releases the money.
Every pickup ends in a signed receipt anyone can verify (npx proof-of-handoff).

How we built it

An Alexa custom skill (ASK SDK) and a web app share the same MCP tools (spec 2025-11-25). A Strands agent on Amazon Bedrock (Nova 2 Lite) negotiates, running on Bedrock AgentCore Runtime. A Policy Kernel decides money, address and approvals. AWS KMS signs receipts, and one Lambda alone can decrypt the address. CDK deploys it all.

Challenges

Alexa+ add-on tooling is partner-only, so we built a real custom skill on the same tools. Ring's Playground sends no webhooks, so we built a signed simulator and use a phone as the camera. In a 300-attack red team, Stoop leaked 0 addresses; a plain agent leaked 57.