A2A capability discovery does not grant payment authority.
The older A2A page advertised x402/1.0 and XRPL-oriented payment headers. Those instructions are retired from current ScriptMasterLabs authority.
Current rule
Discover the selected capability, call its exact target resource, read the fresh PAYMENT-REQUIRED challenge, and let the caller decide whether to create the matching PAYMENT-SIGNATURE.
Current SML paid-resource defaults are Base mainnet eip155:8453 and USDC. A 402 challenge or signature is not settlement proof.