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Use the dedicated x402 tools only when a requested external URL returns an x402 payment challenge.
1

Estimate the external request

Call estimate_x402_outbound_payment with the exact URL, HTTP method, optional request body, and requested fiat funding asset. The tool validates the challenge and creates a durable outbound intent without moving funds.
2

Review and confirm

Show the external USDC requirement, exact fiat amount, fees, pay-to address, and confirm_before. Obtain explicit confirmation.
3

Start fiat funding

Call confirm_x402_outbound_payment with the returned intent ID and confirmed_by_user=true. Follow the server-generated on-ramp instruction.
4

Track the durable intent

Poll get_x402_outbound_payment until terminal. Use list_x402_outbound_payments to recover an existing intent when its ID is unknown.
Outbound x402 currently supports live fiat on-ramps only. Do not construct an x402 header, EIP-3009 authorization, transaction, or signature locally. A USDC transaction hash alone does not prove that the external resource accepted the payment; require the durable intent to report completed and successful=true.