There’s a catalog at x402engine.app that lists every API accepting x402 payments. It’s at 45 and counting.
Most people still think of x402 as a protocol spec. It’s past that. There’s an actual ecosystem — data APIs, compute endpoints, content services — all accessible via a simple payment challenge over HTTP. No API key registration. No OAuth flow. No subscription management. You hit the endpoint, settle the payment, get the response.
What makes the catalog interesting isn’t the number. It’s who can use it. Any client that can sign a payment authorization can access any of these APIs autonomously. That includes AI agents.
This is a different kind of infrastructure than what we’ve been building for agents. Most agent tooling is about capabilities — what can the agent do? x402 is about agency — what can the agent buy? An agent with a wallet and an x402-compatible runtime can navigate this catalog the same way a person navigates a website. Except it settles in USDC, on-chain, without asking anyone.
The catalog is early. Most entries are small. But the shape of it is clear: a marketplace of capabilities that agents can access programmatically, at cost, without human-in-the-loop authentication.
That’s not a prediction. It’s already there.