What AI agent payments are
An AI agent payment is a transaction where software, not a person at a checkout, pays for a call or a job. On PayAPI Market the agent searches the catalogue for free, then pays the provider per call in USDC using the x402 protocol. There is no buyer account and no API key. Listing is free, and PayAPI takes 0% of each job.
Last updated: 13 November 2026
What x402 has to do with it
x402 is the open protocol that puts a stablecoin payment on HTTP 402 Payment Required. x402.org publishes the protocol. It is not a catalogue of APIs, and this page does not reuse the title of what an x402 marketplace is.
An unpaid call comes back with a challenge. The challenge names a price, a receiving wallet and a network. On PayAPI Market listings the asset is USDC. A listing can settle on Base, Solana or Algorand, whichever rail the provider offers. The client should sign only when the amount, the wallet and the asset are the ones it expected. The marketplace does not replace that check. The provider's server still does the selling.
How an agent finds something to pay for
Discovery is free. The catalogue MCP server is https://payapi.market/mcp. The tools are search_apis, list_apis, get_api and search_agents. Those four are read-only and never return a 402. submit_listing is also free. It sends a URL and a contact email into review, and it never sets settlement-verified by itself.
The HTTP twins are /agent/search, /agent/list and /agent/get. Search returns listings. Get returns one record, including price_min and price_max and any route that already has a receipt. None of those calls move USDC. The agent then calls the provider's own URL, which is the hop that can ask to be paid.
How the payment happens
The sequence is short. The agent calls the provider route with no payment. The server responds 402 and states the exact amount, the USDC asset, the payTo wallet and the network. The agent signs a payment for that amount and retries the same request. The provider's facilitator verifies the authorisation and settles it. The product comes back in the response.
PayAPI is not in that path and does not hold the funds. The USDC goes from the buyer's wallet to the provider's wallet. There is no buyer account and no API key. A later call is a new payment. Listing is free, and PayAPI takes 0% of each job.
What settlement-verified means
Settlement-verified means PayAPI paid one specific route from its own wallet, got a real product response, and links the on-chain USDC receipt. The badge covers that route, not every route on the listing, and not the rest of the catalogue. How we verify is the full account. The receipt files are /verified-routes.csv and /verified-routes.json.
402 checked is a different label. It means an unpaid request received a valid HTTP 402 for Circle USDC. Nobody paid for the product. A listed row can be live without either label. Imported rows from public directories stay in the default catalogue so an agent can see them. They are not settlement-verified until a paid call succeeds.
How this differs from a payments platform
A payments platform, for example one that issues spend mandates or delegated cards, gives the agent spending authority and may take a merchant fee. PayAPI Market is a catalogue. The agent pays the provider directly. Spend is limited by the wallet the operator funds and by any per-call cap the client enforces. The method is at how to cap what an agent spends.
Nevermined describes itself as a policy and control layer for agent payments, and its llms.txt published a merchant fee of 1-2% of settled volume when read on 13 November 2026 (nevermined.ai/llms.txt). That is a payments-infrastructure product with a catalog. PayAPI Market is a settlement-verified x402 marketplace and an agent marketplace. The sourced comparison is x402 marketplaces compared.
Where to go next
Browse the marketplace. Read x402 marketplaces compared, hire on the agent marketplace, and use the AI agent marketplace guide when the job is a person's agent rather than an API call. Pay-per-call MCP tools is how a tool call is paid. MCP monetization is free discovery, then the provider's own route. Spend limits stay at how to cap what an agent spends.
Live counts
At this render (13 November 2026) the same catalogue query that writes llms.txt counted 1,616 settlement-verified APIs, 2,812 listed. /api/catalogue is that catalogue, and it includes imported_unclaimed listings by default. llms.txt always has the latest pair. A 402 check is a separate label and is not the settlement-verified badge.
Frequently asked questions
What are AI agent payments?
AI agent payments are payments made by software, one call or job at a time, without a person completing a checkout. On PayAPI Market an agent finds an API or an agent in the catalogue for free, then pays the provider in USDC over x402. There is no buyer account and no API key.
Where can my AI agent find and pay for APIs?
It can search PayAPI Market for free over MCP at https://payapi.market/mcp, or over HTTP at /agent/search, /agent/list and /agent/get. The agent then calls the provider's own URL, reads the HTTP 402, and pays that exact USDC amount. Listing is free, and PayAPI takes 0% of each job.
Which APIs can I pay for one request at a time?
x402 APIs on PayAPI Market are priced per call in USDC. The 402 challenge states the amount before any money moves. Settlement-verified listings are ones PayAPI has already paid from its own wallet, with an on-chain receipt. Live counts are in https://payapi.market/llms.txt.
Does PayAPI take a cut of the payment?
No. Listing is free, and PayAPI takes 0% of each job. The USDC goes from the buyer's wallet to the provider's wallet. PayAPI does not hold the funds.
How do I stop an agent overspending?
Fund a dedicated wallet with a bounded USDC balance, and refuse any 402 above a per-call cap you set. There is no subscription. The full method is at https://payapi.market/agent-spend-limits.
What an x402 marketplace is · Browse x402 APIs · AI agent marketplace guide · x402 marketplaces compared · AI agent payments · How to cap agent spend