Inspect the challenge
A client should verify price, asset, network, recipient, expiry and resource binding before it signs or pays.
AGENT PAYMENT FIELD GUIDE · 2026
x402 Protocol Guide
Understand the x402 protocol and HTTP 402 payment flow for APIs, content and AI agents: discovery, payment requirements, authorization, settlement and accepted delivery.
SML-X402-001$29 ONE TIMEINSTANT PDF DELIVERY
THE OUTCOME
See the full machine-payment loop and the evidence needed between a 402 challenge and accepted delivery.
Primary search intent: x402 protocol guide
WHAT YOU WILL LEARN
A compact, evidence-first field guide.
- The request → 402 → payment → retry → delivery sequence
- What clients should verify before authorizing payment
- Why settlement and accepted delivery are separate evidence stages
- Operational controls for price, network, recipient, replay and failure handling
INSIDE THE GUIDE
Practical concepts and decision checks.
Authorize narrowly
Payment policy should cap amount, restrict destinations and bind approval to the intended request.
Separate settlement from delivery
A successful transfer proves value moved. It does not prove the paid API returned a correct, complete response.
Retain evidence
Request identifiers, payment evidence, response status and acceptance checks support retries, disputes and audits.
PRIMARY SOURCES
Built from sources buyers can inspect.
The PDF includes source notes. These public references provide the governing background and current official context.
x402 documentation →x402 specification →FAQ
Before you buy.
What is x402?
x402 is an open payment protocol that uses HTTP 402 Payment Required to let services present machine-readable payment terms.
Does the guide provide a wallet?
No. It explains the protocol and operational controls; it does not custody funds or sign transactions.
Does payment prove delivery?
No. Settlement and accepted delivery should be verified separately.
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Buy x402 Protocol Guide — $29Educational information only. No personalized investment, legal, tax, regulatory, cybersecurity or business advice. No ranking, citation, performance or financial outcome is guaranteed.