x402 Guides (12 published)

AgentIndex publishes 12 long-form guides for builders working with the x402 payment protocol. The directory pages show which services accept x402 payments; the guides explain the protocol itself — where the HTTP 402 status code came from, how a paid request moves from challenge to settlement, and how to price an API that autonomous agents can pay for without accounts or API keys.

Every guide is written against the live directory dataset and links straight into it: category hubs, chain hubs, facilitator profiles, and price-band pages. The questions at the end of each guide are answered in plain language and marked up as structured data, so readers and answer engines get the same facts. New guides join the collection with the dataset refresh cycle, and each guide's Related box points to the directory pages that back its claims.

• What Is x402 Protocol? Open Payments for AI Agents

  x402 is an open payment protocol originated by Coinbase that activates HTTP 402 for stablecoin micropayments. Definition, origins, and ecosystem data.

• How Does x402 Work? The Payment Flow, Step by Step

  Step-by-step walkthrough of the x402 payment flow: the 402 challenge, the signed USDC payment, facilitator verification and settlement, and fulfillment.

• Monetize AI Agent API: Per-Request Pricing with x402

  How to charge AI agents per API call with x402: per-request pricing from 100 live services, chain and facilitator choices, and realistic price points.

• HTTP 402 Explained: The Status Code That Charges You

  HTTP 402 Payment Required sat reserved in the spec for decades. Read the status code's history, why nothing ever used it, and how x402 finally puts it to work.

• What Is a Payment Facilitator in x402?

  In x402, a payment facilitator verifies signed payments and settles them on-chain so servers skip running nodes. The role explained, plus the landscape.

• x402 vs Stripe: Two Payment Rails for Different Buyers

  x402 vs Stripe compared fairly: accountless per-request USDC payments for AI agents versus account-based fiat billing, subscriptions, and invoices for humans.

• x402 vs L402: Two Protocols That Answer HTTP 402

  x402 vs L402, the two protocols that activate HTTP 402 for paid APIs: stablecoin settlement on Base and Solana versus Lightning invoices with macaroons.

• x402 on Base: Inside the Directory's Default Chain

  What x402 on Base looks like in the directory: all 87 listings, the category mix, prices from $0.0001 to $10 per request, and the facilitators settling them.

• x402 on Solana: Small Catalog, Micro Prices

  What x402 on Solana looks like: 13 listings heavy on data APIs and MCP tools, prices from $0.00001 to $0.54 per request, and the four settling facilitators.

• x402 Facilitators Compared: The Settlement Landscape

  The x402 facilitator landscape compared: seven operators, honest listing counts from coinbase's 83 down to single listings, and how to choose between them.

• x402 Glossary: The Eight Terms That Matter

  An x402 glossary in plain language: the protocol, HTTP 402, facilitators, stablecoins, micropayments, pay-per-request, MCP, and settlement, defined and linked.

• The State of x402: What 100 Live Services Show

  The state of x402 measured from the live directory: 100 services by category, chain, facilitator, and price band, and what the mix says about the ecosystem.