x402 Preflight: HTTP readiness check for x402 API buyers, sellers, and listing agents. It probes a target paid URL plus

x402 Preflight: HTTP readiness check for x402 API buyers, sellers, and listing agents. It probes a target paid URL plus same-origin /.well-known/x402 and /openapi.json, /llms.txt, /agent-catalog.json, and /.well-known/ai-plugin.json, then returns payment-challenge signals, parsed payment metadata, comparable Bazaar resources, pricing context, discovery health, LLM/catalog readiness, conversion-readiness verdict, score, issues, and next actions. No payment is made to the target endpoint.