x4PayAPI Market ยท Marketplace

List your API

Turn your data or tool into a pay-per-call API for AI agents. It takes a few minutes: add your details and your API, then review. No payment integration to build: agents pay you per request in USDC on Base, Solana or Algorand via the x402 protocol.

Listing is free. Providers keep 100% of what the call earns.

Want the provider playbook by email? Use the box on the homepage.

2317 live APIs and 29671 endpoints are already listed on PayAPI Market.

How listing works

  1. Your details - your name, email, and USDC payout wallet on Base.
  2. Your API - name, description, category, base URL, and price per request.
  3. Review and submit - confirm your details and submit for verification.

Check before you submit

The form calls your paid route unpaid before it creates a row, so a URL that does not already answer a Base x402 challenge is refused on the spot.

Paste the paid route that already returns HTTP 402, not the homepage.

If this URL does not return HTTP 402 to the wallet you typed, the form will not create a listing.

  1. curl -i the paid route
  2. You should see HTTP 402
  3. extra.name is USD Coin and payTo is your wallet
  4. Then submit

Questions providers ask

What happens after I submit?

Automated checks run first (host durability, a real 402, payTo matches the wallet you entered). Then a human reviews. You get one email with the result. Live, needs a fix, or cannot test. There is no separate "we got it" mail.

Do I pay to list?

No. Listing is free. Providers keep 100% of each settled call.

What will you pay on my API?

One cheap canary on one route, up to $0.10, from our wallet. If that call returns real product and the money landed on your listed wallet, the listing can go live with a settlement-verified badge. The badge is that receipt, not a health ping. Tests priced above $0.10 are not paid from PayAPI's canary wallet, and a payment from another wallet is not accepted. Send the test price plus 20% in USDC on Base to 0x171d8021b98c53DCbB3c9C30CBbBeb1b01850fCA. We will email you once the top-up arrives, then run one paid test of this route. A listing depends on that test passing review.

What gets bounced?

Ephemeral hosts (trycloudflare, ngrok, sslip, random zrok shares). Prepaid credits instead of per-call x402. A challenge payTo that is not the wallet on the form. A second listing that is the same product or a sub-path of one already live. extra.name must be "USD Coin" on Base USDC or settlement fails.

What do I need on the form?

A durable URL, the paid route, a working example request, a Base USDC wallet you control, and a price that matches the live 402. We test the listing with that example request before it can be badged settlement-verified. Wallet is required. Sandbox and tunnel hosts are blocked.

Why was my URL rejected?

We call it unpaid before a row is created. Homepage, AppDeploy/Floot/Bonto shells, and a 402 with no Base USD Coin challenge all fail here. The paid route has to 402 to your wallet.

Any funded Base wallet that signs the 402 must receive the product. No allowlist, no API key, no signup.

How do agents find it once it is live?

Search is free at https://payapi.market/mcp

Put this in a README: url https://payapi.market/mcp

Start listing - free · See pricing · Browse the marketplace

Last updated: 2026-10-30