x402 on HPP

x402 is an open payment protocol that revives the long-dormant HTTP 402 Payment Required status code. It lets any HTTP endpoint charge for access with onchain stablecoins — no API keys, no accounts, no manual invoicing. A client requests a resource, receives a 402 with machine-readable payment terms, pays by signing a stablecoin authorization, and retries. Settlement happens onchain.

HPP runs production x402 facilitators on both its Mainnet and Sepolia networks, so you can monetize an API — or pay for one — using USDC.e with a few lines of code.

It's built for agentic payments: an AI agent can discover a price and pay it autonomously — keyless, wallet-less, and non-custodial. The fastest way to see that is Pay from an AI agent, which gives Claude, Cursor, or any MCP host a capped wallet with no code.

Why x402

• Built for agents and machines. Payment is a single signed message on a standard HTTP response. No human-in-the-loop, no dashboard signup. AI agents can discover a price and pay it autonomously.
• No accounts, no custody. Payment moves from the buyer's wallet to the seller's payTo address; HPP's facilitator never custodies funds — it only verifies the signature and submits the settlement transaction (a direct transfer for exact, or a Permit2 transfer for upto).
• Stablecoin-native. Prices are quoted in USDC.e. What the buyer signs is what the seller receives.
• Open standard. x402 is maintained by the x402 Foundation, and HPP uses the same @x402 SDK that works on Base, Polygon, and others — pointed at HPP's networks and facilitator. One small setup step registers USDC.e as HPP's default asset (shown in the quickstarts).

What HPP provides

Piece	What it is
Facilitators	Hosted verify / settle services for HPP Mainnet (facilitator.hpp.io) and HPP Sepolia (facilitator-sepolia.hpp.io). See Facilitator.
Networks	HPP Mainnet (eip155:190415) and HPP Sepolia (eip155:181228), recognized natively by the @x402 SDK. See Networks & Token.
Token	USDC.e (Bridged USDC) at 0x401eCb1D350407f13ba348573E5630B83638E30D on both chains.
Schemes	exact (EIP-3009) and upto (Permit2 with optional gasless settlement). See How it works.

Choose your path

Pick your side of the payment.

💸 I want to pay for services (buyer)

From…	Start here
an AI agent — Claude, Cursor, … (no code)	Pay from an AI agent
my own code	Quickstart: Buyers

🏷️ I want to charge for my service (seller)

How	Start here
Put a price on an HTTP endpoint (SDK)	Quickstart: Sellers
One command, no server code	hpp-x402 serve — see the agent guide

📖 Learn the concepts

• How it works — the 402 flow, the three roles, and the payment schemes.
• Service directory — the curated catalog buyers and agents discover.
• Networks & Token — chain IDs, RPC endpoints, and the USDC.e asset.
• Facilitator — endpoints, supported schemes, gasless settlement, and self-hosting.