x402
x402 revives HTTP 402 Payment Required as an agent-native payment flow: the server states its price, the client pays, the request completes.
Why it matters
For content and APIs that cost money to produce, per-request payment beats a subscription an agent cannot sign up for.
Pass criteria
Payable routes answer HTTP 402 with x402 requirements, or a discovery document is published.
Every request the check makes is recorded (URL, method, response status, relevant headers and a body preview) and shown under the check in your results.
How to implement it
Support x402 protocol for agent-native HTTP payments
Payable routes answer HTTP 402 with x402 requirements, or a discovery document is published.
The step-by-step implementation prompt is part of the Pro plan.
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See whether this check passes on your domain, along with the other 21.
Related checks
MPP
An OpenAPI document annotates payable operations with x-payment-info.
UCP
/.well-known/ucp declares protocol_version and at least one service.
ACP
/.well-known/acp.json declares protocol.name, api_base_url, transports and capabilities.services.
AP2
The A2A Agent Card advertises an AP2 extension with role information.