x402 overview

What is x402?

x402 is an open, HTTP-native payment standard built on HTTP's long-reserved 402 Payment Required status code. It lets software pay software on a per-request basis — no API keys issued to agents, no subscription management, no billing portals. The payment itself is the credential.

Payzum implements x402 as the payment and settlement layer for your API. When an AI agent calls a payzum-gated endpoint, payzum:

1. Responds with 402 Payment Required and the exact price (USDC on Base).
2. The agent constructs a signed EIP-3009 authorization and retries the request with an X-PAYMENT header.
3. Payzum validates the authorization through a facilitator (Coinbase CDP for mainnet or a free testnet facilitator for development).
4. On success, payzum proxies the request to your origin API and returns the response to the agent.

Settlement goes directly to your wallet — payzum never holds the funds.

When to use Payzum for Agents

Use x402 when you want to monetize an API or data endpoint for autonomous AI agents without requiring them to register, receive an API key, or maintain a billing relationship:

• Data APIs — real-time prices, market data, on-chain analytics
• Inference endpoints — model inference, embedding generation, classification
• Tool calls — any HTTP-accessible capability that an AI agent might call during a task

The x402 model is especially well-suited for agentic workloads where the caller is software, not a human, and must be able to discover, evaluate, and pay for access programmatically.

How it fits with the rest of payzum

Payzum for Agents runs alongside payzum's standard invoice and payout features. It is a separate subsystem with its own route configuration; it does not affect your existing payment flows.

Settlement is crypto-in / crypto-out, consistent with payzum's broader model. Payments arrive as USDC on the Base network (EVM, ERC-20). The asset and network are fixed for the MVP — multi-asset support is planned for a future release.

Key concepts

Protected routes

A protected route is a mapping you configure in the Payzum dashboard. It ties a public slug (the path agents call) to your origin API URL and sets the per-call price in USDC. Payzum intercepts requests on that slug, runs the x402 handshake, and forwards authenticated requests to your origin.

Facilitator

A facilitator is the service that verifies and settles the EIP-3009 payment authorization. Payzum supports two:

• Coinbase (CDP) — mainnet: Uses your own Coinbase Developer Platform API key to settle real USDC on Base. Gas and per-transaction costs are billed to your CDP account. See Coinbase pricing for current rates.
• Testnet — free: Settles on Base Sepolia via the free public facilitator. No real funds move. For development only.

The BYOK (bring-your-own-key) model means payzum never holds funds or absorbs settlement risk.

Discovery catalog

Routes you mark as discoverable are listed in payzum's discovery catalog. Agents can query this catalog to find endpoints by category, title, and description. When you use the Coinbase (CDP) facilitator, discovery metadata is also published to the ecosystem-wide x402 Bazaar via the CDP facilitator.

Settlement asset

The MVP settlement asset is USDC on Base:

| Property | Value | |---|---| | Asset | USDC (ERC-20) | | Network | Base (mainnet) | | Contract | 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 | | Precision | 6 decimal places |

Prices you enter in the dashboard (e.g. 0.01) are converted to atomic units internally (e.g. 10000). The payment authorization the agent sends carries the atomic amount.

Next steps

See x402 integration for step-by-step instructions on configuring protected routes, setting up a facilitator, and making your endpoints discoverable.