x402 ping: cheapest end-to-end test of an x402 payment on Base. x402 payment test and ping: one call with no required parameters returns server time (ISO 8601 and Unix ms), a request id, the seller payTo, chain id and an echo of your optional text, only after a real settlement. Use this when an agent needs to prove its payment flow works, measure round-trip latency or run a cheap scheduled canary against a live seller. No upstream, no model inference; paid rou Price: 0.001 USDC per call (x402 on Base). Without payment_signature it returns the payment requirements. Free sample: textokit_sample.