x402 API directory: how to find and check x402 APIs
An x402 API directory is a catalogue an agent searches before it calls a paid endpoint. PayAPI Market is an x402 marketplace and an AI agent API marketplace. Discovery is free, and a settlement-verified listing is one we paid ourselves. The unpaid 402 states the price, network and payTo address before any payment.
Last updated: 30 October 2026
What is an x402 API directory?
An x402 API directory is a catalogue an agent searches before it calls a paid endpoint. It should name the API, the price range, the URL and how the row was checked. PayAPI Market is that directory and an x402 marketplace. Search is free. Listing is free and providers keep 100%. See llms.txt.
The agent then calls the provider directly. PayAPI Market is not in the payment path. Search is also free at https://payapi.market/mcp and at /agent/search. A page that only repeats what the seller typed is a phone book. This one says how the row was checked.
The same catalogue query that writes llms.txt currently counts 1,134 settlement-verified APIs, 2,331 listed.
Can an agent see the price before paying?
Yes. Call the endpoint without a payment. The HTTP 402 response states the price, the network and the payTo address before any payment is made. Nothing has been signed. The agent can stop, or it can sign a USDC payment for that exact challenge and retry. Paying without an API key walks through the same loop.
On this AI agent API marketplace, get_api returns price_min and price_max for the listing as well. Those figures are read from the live 402, so the catalogue and the challenge should agree. The challenge on the call is the amount the agent will be asked to pay. A listing page and the guide to paying without an API key walk through the same loop.
Networks are part of that challenge. Listings accept USDC on Base. Some also accept USDC on Solana or Algorand on the same route, and the 402 names the network. An agent should match the network to the wallet it holds before it signs.
What is the difference between a 402 check and settlement-verified?
A 402 check means an unpaid request received a valid HTTP 402 for Circle USDC. It shows that an endpoint asks to be paid. Settlement-verified means we paid one named route, received real product back, and link the on-chain USDC receipt. The badge is that route, not demand. How we verify defines both checks.
Settlement-verified means we paid one named route from our own wallet, received real product back, and link the on-chain USDC receipt. The badge covers that route, not every route on the listing. How we verify defines the term, compares it with a 402 check and with payment-provider settlement, and says what the badge does not prove. It is a paid check, not a claim about demand.
How does an agent search this directory?
Add https://payapi.market/mcp to any MCP client that speaks streamable HTTP. search_apis, list_apis and get_api are free and never return a 402. get_api returns the base URL, the price range, the network and, when the provider supplied one, an MCP endpoint. Treat that URL as a claim. We do not probe it.
Plain HTTP is the same catalogue. /agent/list defaults to settlement-verified listings. Pass verified_only=false to include live listings that have not been paid yet. They are labelled, not mixed in quietly. Humans can browse the marketplace and the 2027 shortlist, which is picked from the settlement-verified catalogue and states its rules.
Which other public x402 directories can an agent use?
Several public sites also index x402 endpoints, and they are not the same product. The table says what each page publishes, with a link we opened and the date we opened it. We do not copy their totals onto this page. A frozen number is how directories start to disagree. Protocol background is at x402.org.
| Directory | What the public page says | Source | Checked on |
|---|---|---|---|
| PayAPI Market | An x402 marketplace. Discovery is free. A settlement-verified listing is one route we paid, with the receipt linked. Listing is free and providers keep 100%. | llms.txt | 30 October 2026 |
| x402 List | An agent-first directory of x402 services. It publishes the catalogue as JSON, including uptime, and describes a paid-probe tier separately from a 402 handshake probe. | x402 List | 30 October 2026 |
| the402 | An endpoint directory that calls routes and reports whether they answer 402. The page says it parses the payment challenge and does not complete a payment. | the402 | 30 October 2026 |
| x402 Directory | A browseable index of paid x402 endpoints. The services page attributes its uptime and compliance figures to x402 List. | x402 Directory services | 30 October 2026 |
| Coinbase CDP Bazaar | A discovery catalogue of services indexed through the CDP Facilitator. The docs say indexing runs after a payment settles, and that agents can search the catalogue over HTTP or MCP. | CDP buyer discovery docs | 30 October 2026 |
What does a directory row not prove?
A directory row is not a promise that the next call will succeed, and it is not a measure of buyer demand. Use the receipt date on a settlement-verified listing, set a spending cap, and read the 402 before you sign. Sellers can list an API for free and keep 100%. The badge limits are on how we verify.
Frequently asked questions
What is an x402 API directory?
It is a catalogue of APIs that accept x402 payments, so an agent can find an endpoint and read its price before calling it. PayAPI Market is an x402 marketplace that publishes that catalogue for free over MCP, HTTP and llms.txt.
Can an agent see the price before paying?
Yes. The unpaid HTTP 402 response states the price, the network and the payTo address before any payment is made. get_api also returns price_min and price_max for the listing, read from that live 402.
How is PayAPI Market different from a list of 402 endpoints?
A 402 check shows that an endpoint asks to be paid. Settlement-verified means we paid one named route from our own wallet, got real product back, and link the on-chain receipt. The badge is that paid check, not a claim about demand.
Which networks does the directory include?
Listings accept USDC on Base. Some also accept USDC on Solana or Algorand, and the unpaid 402 names the network. We count a network as verified for a listing only after we have paid a route on it.
Does it cost anything to be listed?
Listing is free and providers keep 100% of each paid call. Searching the directory is free. The caller pays the provider's own per-call price, shown in the 402 before any payment is made.
Sources
- PayAPI Market llms.txt
- How we verify
- x402.org
- x402 List
- the402
- x402 Directory
- CDP buyer discovery docs
Related: marketplace · for agents · FAQ · how we verify
How to find an x402 API, read the price before paying, and tell a settlement-verified listing from a 402 check on this AI agent API marketplace.