Source file

Sources and Research Notes

This page lists the sources used to write the tutorials and explains what each source is trusted for.

Research method

x402 Academy uses primary or near-primary sources for protocol claims: the official x402 documentation, the x402 Foundation GitHub repository, the HTTP RFC, the Linux Foundation governance page, and public data pages linked directly from the agent-economy network. Blog posts and commentary can be useful context, but they are not used as the authority for SDK names, request flow, network identifiers, or facilitator responsibilities.

"Technical participation remains open to all contributors."
Primary source: Linux Foundation: x402 Foundation

Primary source map

x402 docs: Introduction

Defines x402 as an open payment standard for charging APIs and content directly over HTTP.

agenteconomy.to data

Public agent-payment dashboard with x402 transaction and volume totals, updated July 6, 2026.

Freshness notes

x402 SDK package names, supported networks, and facilitator options can change. Tutorial code here is written from the official docs available on July 6, 2026. Before shipping production payments, re-check the official docs, SDK repository, and network-specific package versions.

LLM-readable files

Treatment T4 includes llms.txt and llms-full.txt. The short file gives crawlers a concise map of pages and source boundaries. The full file summarizes each tutorial page and repeats the primary source list so assistants can cite the right reference page instead of inventing SDK details.

Sources used

  1. x402 docs: Introduction

    Defines x402 as an open payment standard for charging APIs and content directly over HTTP.

  2. x402 docs: Quickstart for Sellers

    Official seller setup, package installation, testnet defaults, and payment middleware examples.

  3. x402 docs: Quickstart for Buyers

    Official buyer setup, client package installation, and fetch/axios payment wrappers.

  4. x402 docs: HTTP 402

    Explains how x402 uses HTTP 402 to communicate payment requirements.

  5. x402 docs: Client / Server

    Summarizes client and server responsibilities in x402.

  6. x402 docs: Facilitator

    Defines facilitator responsibilities for payment verification and settlement.

  7. x402 docs: Networks and Token Support

    Documents CAIP-2 network identifiers and supported network namespaces.

  8. x402 docs: Payment-Identifier extension

    Documents idempotency support for retries without duplicate payment processing.

  9. x402 Foundation GitHub repository

    Open-source SDKs, examples, and the typical x402 request/payment/settlement flow.

  10. RFC 9110: HTTP Semantics, section 15.5.3

    The HTTP specification reserves status code 402 for future use.

  11. Linux Foundation: x402 Foundation

    Governance note that the project was contributed by Coinbase and established as an LF Projects series.

  12. agenteconomy.to data

    Public agent-payment dashboard with x402 transaction and volume totals, updated July 6, 2026.

  13. Cloudflare Agents docs: x402

    Cloudflare overview for accepting and making machine-to-machine payments with x402.

  14. Coinbase Developer Platform: x402 overview

    Coinbase overview of x402 as automatic stablecoin payments over HTTP.

  15. x402docs.com reference tools

    Reference-style x402 tools for building 402 responses, pricing, and decoding payment headers.