The status is a signal
HTTP 402 indicates payment is required but does not by itself define asset, network or proof format. x402 defines them — see the x402 payment protocol.
Agent Commerce & Security · PDF FIELD GUIDE · 2026
HTTP 402 Payment Required Explained
HTTP 402 Payment Required Explained (SML-X402-002) is a four-page SCRIPTMASTERLABS field guide, $29 one-time, covering HTTP 402 status semantics, payment challenges and implementation boundaries. Its core model: HTTP 402 signals payment is required but defines nothing by itself — terms must be machine-readable, retry must be bound, and delivery stays separate from transfer.
Status semantics, payment challenges and implementation boundaries
SML-X402-0024-PAGE PDF$29 ONE TIMEINSTANT DELIVERY
THE OUTCOME
What role does HTTP 402 play in usable machine payments?
HTTP 402 indicates payment is required but does not by itself define asset, network or proof format — the additional protocol decisions this guide covers.
Use this guide to: Understand HTTP 402 and distinguish a payment challenge from authorization and successful delivery.
CORE MODEL
What are the four ideas before action?
Four ideas: the status is a signal, terms must be machine-readable, retry must be bound, and delivery is separate.
Terms must be machine-readable
Price, recipient, expiry, resource and payment method need unambiguous representation.
Retry must be bound
Payment proof should attach to the intended request and resist replay or substitution.
Delivery is separate
A valid transfer does not prove that the requested resource was correct or accepted.
ACTION CHECKLIST
What are the six steps of the review process?
Specify price and denomination, bind terms to resource and expiry, validate network and recipient, protect proof against replay, return deterministic errors, and record payment and delivery evidence.
- Specify price and denomination
- Bind terms to resource and expiry
- Validate network and recipient
- Protect proof against replay
- Return deterministic errors
- Record payment and delivery evidence
PRIMARY SOURCES
How do you verify the moving parts?
The PDF includes a source map and explicit research boundary. Product and regulatory details can change; current official material controls.
x402 protocol documentation →x402 specification repository →Model Context Protocol specification →OWASP API Security Top 10 →TRUTH BOUNDARY
Protocol support and settlement finality vary by implementation and network.
AI tools assisted drafting and layout. SCRIPTMASTERLABS is responsible for editorial structure and source selection. No personalized investment, legal, tax, medical, regulatory, advertising or cybersecurity advice.
FAQ
What should you know before you buy?
What format is this product?
A four-page PDF field guide delivered immediately after successful Stripe Checkout.
Is this a subscription?
No. It is a one-time purchase.
Does this guarantee a result?
No. Protocol support and settlement finality vary by implementation and network.
What is included in this PDF?
4 pages in a fixed-layout PDF: HTTP status semantics, payment challenges and delivery verification. This is a compact field guide with review checks and source notes.