HTTP 402 is 'Payment Required': a status code the web specified in the 1990s and never used, because there was nothing to pay with. It sat reserved until machine-to-machine payments gave it a job: a server answers 402 with a price, a client answers with payment, the request proceeds.
The code matters because it standardizes the handshake: any client, any server, one meaning. AI agents buying API calls, meters buying electricity, cars buying charging: 402 is the door they knock on.
U.CASH implements 402-native payments for machine and agent flows: agents hold keys, answer 402 challenges, and pay per call, with the same non-custodial settlement as every other rail.
Every term behind the rails, the assets, and the settlement.