1. Request
An agent requests a paid API resource.
Internet-native payments
Software can pay for the capabilities it needs.
x402 is an open protocol for HTTP-native payments. Instead of requiring a traditional subscription or long-lived customer account, a resource can require payment as part of the request flow.
x402
2. Payment
The payment requirement is handled through the x402 flow.
3. Resource
Once paid, the service returns the requested structured result.
Where we fit
x402 is the rail. Preflight Stack is the utility layer.
Preflight Stack builds focused capabilities on top of the payment rail: dependency preflight decisions, random selection, and temporary artifact handoff between systems that do not share storage.
Why it matters
- Pay-per-request economics
- Useful for machine-to-machine interactions
- No need to bundle every capability into one platform
- Services can stay small, composable, and easy to understand
Machine discovery
Clear paths for agents and crawlers.
Human service pages explain when to use each capability. Machine-readable resources point clients to the live contracts without guessing.
Agent index
Start with the concise root llms.txt, then follow clean Markdown page links.
API contracts
OpenAPI documents on each service origin remain the authoritative request and response contracts.
x402 manifest
The well-known capability manifest enumerates exact paid resource URLs and methods. It is discovery metadata, not an endorsement or security guarantee.