How an agent pays for a VIN
What do you POST?
An agent sends POST /api/v1/nodes/vin-decode with a JSON body. The only field is vin. HTTP 402 means Payment Required. TollNode uses it to return a USDC quote before any vehicle data. The quote uses x402 version 2: scheme exact, asset USDC, network as a CAIP-2 id.
When is the call free?
A VIN that fails the character set, length, or (for North America) the ISO check digit comes back as 400. That call is not a sale.
What does 402 mean today?
A VIN that passes validation comes back as 402 with a quote of $0.005USDC on Base. The agent's wallet signs that amount and retries. TollNode decodes the VIN and only then collects the payment, so a failed decode costs nothing.
What if NHTSA is down?
When NHTSA is down, a paid call should return 502 and should not settle. The demo on the VIN decoder API is the path that talks to NHTSA today. The full request and a sample quote are in the machine contract.