An AI agent cannot sign up for your API. It has no email, no card, and no way to accept your terms. What it can do is pay a fraction of a cent per call, unattended, from its own wallet.
Serve an x402 challenge, register your origin, and the index routes matching buyer tasks to you. Money moves buyer wallet to your wallet. We never hold it, and nothing is deducted from your price.
| listing fee | $0 |
|---|---|
| deducted from sellers | 0% |
| signup / account | none |
| review queue | none |
| who holds your funds | you do |
| you keep your paywall | yes |
| how we earn | buyer side only |
Settlements land on chain, but which tool an agent bought never does - so this ledger cannot be reconstructed from a block explorer by anyone, including us. It is the one dataset in the x402 ecosystem that only the seller who served the call can see. Here are the lanes agents spend most in, in order. The numbers behind them are a tool, not a marketing page.
| # | lane | what agents buy in it |
|---|---|---|
| 01 | Hashing & encoding | sha256/sha512 digests, HMAC, base64, JWT decoding: called dozens of times inside a single job. |
| 02 | Market & financial data | Live quotes, historical series, Treasury yield curves, SEC company lookups. |
| 03 | Media & documents | Speech-to-text, OCR, PDF parsing, article extraction, browser rendering. |
| 04 | Inference | Cheap chat tiers used inside agent loops, plus embeddings and generation. |
| 05 | Live web search & cited answers | Ranked results, and grounded answers with sources attached. |
| 06 | Crypto & onchain reads | Token prices and metadata, balances, transaction history, gas. |
| the figures | Per-tool purchase counts, distinct buyers, revenue and buyer-diversity - plus each tool's trend against the previous window, over any 1-90 day span. | $0.005 → |
We also log what agents searched for and did not find. Those wish clusters are ranked at /api/demand-radar, tagged by whether agents asked outright or simply failed to discover something that already exists - and flagged when a cluster is within two signals of the build threshold. It is the closest thing to a build list for an x402 seller, and nobody else is sitting on the data.
demand radar → $0.005 per readNot novelty. The heaviest lanes are dull, deterministic and cheap - the calls an agent makes dozens of times inside a single job, where a wrong answer breaks the whole chain. You do not need novelty to sell into that. You need to be callable, correctly priced, and reachable when the router asks.
Return a 402 with your price, asset, network and payTo on the endpoints you want to charge for. Register the origin and the crawler reads your manifest at once, then re-probes it every 30 minutes. From then on the Smart Order Router can send you work, ranked against our own tools on the same terms.
# what a buyer's agent sees HTTP/1.1 402 Payment Required PAYMENT-REQUIRED: eyJ4NDAyVmVyc2lvbiI6Mi… # base64 JSON, decoded: {"x402Version":2,"accepts":[{"scheme":"exact", "network":"eip155:8453","amount":"4000", "asset":"0x833589fC…02913","payTo":"0xYourWallet…"}]}REGISTER YOUR ORIGIN →
If AI crawlers are already taking your content for free, tollbooth is the open answer. Humans browse normally; known bots get a 402 and either pay in USDC or solve a proof-of-work. MIT licensed, one middleware, no CDN lock-in and no merchant of record standing between you and the money.
# express · next.js · cloudflare · proxy · wordpress
npm i agent402-tollbooth
Coinbase Business account? →Gate your crawlers →
There is no dashboard to log into and nothing to wait for. You serve a 402, you tell us where you live, and the crawler does the rest.
Return HTTP 402 Payment Required with your price, asset, network and payTo address on the endpoints you want to charge for. Any x402 middleware does this.
One POST to /api/index/register. No account, no review queue, no waiting on us.
The crawler reads your manifest at once, records your tools and advertised chains, and re-probes it every 30 minutes; health is scored from those probes. Probes are never paid calls.
The Smart Order Router resolves a described task to a listing. Candidates are shortlisted by how well they match the task, then ordered by crawl health, by distinct payers over the last 30 days, by price, by a discovery listing's curated flag and by slug length, shorter first; a judgment model can then pick the one that does the job from that shortlist, or decline them all, and when it is not consulted the shortlist order stands. An accurate description is how you win it.
Buyers pay your wallet directly in USDC. Your settled volume shows up on the public on-chain leaderboard.
curl -X POST \
https://agent402.tools/api/index/register \
-H 'content-type: application/json' \
-d '{"origin":"https://seller.example"}'
Speak MPP? Register your MPP server on the MPP marketplace → (one call, or POST /api/mpp-index/register {"origin", "path"}); dual-stack sellers our x402 crawl already sees answering MPP are picked up automatically.
| manifest | /.well-known/x402 |
|---|---|
| your tools | route · price · description |
| your chains | from the 402 challenge |
| health probe | every 30 minutes, never paid |
| what we never read | your keys or funds |
Already listed and nobody is paying? POST /api/seller-payability buys one call from your own endpoint with our wallet and reports every leg: the 402 decoded, whether a stock client's signature was accepted, the settlement receipt. $0.10. Want the audit first? /api/x402-audit grades any x402 endpoint's payment-security posture from the outside, without paying it. Run it on yourself before you list.
Four surfaces, and the router is the one that matters. A buyer describes a task, the router resolves it to a tool, and it does not care whose tool it is. New sellers get the benefit of the doubt on health rather than being buried until they have a track record.
| Smart Order Router | A buyer describes a task in words; the router resolves it to a tool and runs it. It does not care whose tool it is, and it will buy from an external seller and resell the result to the buyer. | /api/route |
|---|---|---|
| Marketplace directory | Every indexed seller with tool count, advertised networks, last crawl and rolling health - browsable by humans and machines. | /marketplace |
| Per-chain market pages | One page per settlement rail, so a buyer on Solana or Algorand can find sellers who take their chain. | /solana |
| On-chain leaderboard | Ranked by real Base USDC settled. Once you have volume, you get a public row - and the row carries buyer diversity, not just dollars. | /leaderboard |
| + the rest | Ranked by distinct buyers, sales, revenue or buyer-diversity - plus each tool's trend against the previous window, over any 1-90 day span. | $0.005 → |
Advertise every rail you support: each one is another set of buyers who can pay you directly. When the router buys from a seller to resell the result to an agent, it pays the seller on the chain the agent paid on, so it reaches you only on chains you accept; it holds spending wallets for Base, Algorand, Solana and Tempo. Gas is sponsored by the facilitator on EVM chains, so neither side needs the native token.
A buyer who discovers you and pays you directly costs you nothing and earns us nothing. That is most traffic, and it is the point.
We earn when the router buys from you and resells the result to a buyer: the buyer pays us one flat price for the convenience of not integrating you, and we pay you your full advertised price. The margin is the spread, charged to the buyer, disclosed in the router's own pricing tiers.
We would rather write that down than let you find it out. An index that quietly taxed its sellers would deserve the reputation it got.
| ✓ | We never take custody of your funds. Buyers pay your wallet, not ours. |
| ✓ | We never deduct a commission from your advertised price. |
| ✓ | We never require an account, a contract, or a call with sales. |
| ✓ | We never rank you down for refusing the router - direct buyers are yours. |
| ✓ | We publish how the ranking works, and exclude ourselves from our own leaderboard. |
verify in src/x402-index.js →
Nothing. Listing is free, there is no signup and no review queue, and no commission is deducted from your price. Buyers pay your wallet directly and Agent402 never holds seller funds. We earn on the buyer side only, on the spread when the router buys from a seller and resells the result to a buyer.
Four surfaces: the marketplace directory, the per-chain market pages, the Smart Order Router which resolves a described task to a tool, and the public on-chain leaderboard once you have settled volume. Candidates are shortlisted by how well they match the task, then ordered by crawl health, by distinct payers over the last 30 days, by price, by a discovery listing's curated flag and by slug length, shorter first; a judgment model can then pick the one that does the job from that shortlist, or decline them all, and when it is not consulted the shortlist order stands.
Use agent402-tollbooth - the pay-per-crawl mechanism is explained above under "Charge the crawlers instead". It ships as an open MIT middleware for Express, Next.js, Cloudflare Workers, a reverse proxy or WordPress: drop it in front of any site, no rebuild required.
Advertise whichever you support. Agent402 itself accepts 12 rails: USDC on Base, Solana, Polygon, Arbitrum, Monad, Celo, Avalanche, Sei, Optimism, Stellar & Algorand - plus USDG on Robinhood Chain. When the router buys from a seller to resell the result to an agent, it pays the seller on the chain the agent paid on, so it reaches you only on chains you accept; it holds spending wallets for Base, Algorand, Solana and Tempo.
Two paid intelligence tools, both half a cent a read. /api/bestsellers ranks what agents actually pay for across a 500+-tool catalog by distinct buyers, sales, revenue or buyer diversity, with a trend against the previous window. /api/demand-radar ranks what agents asked for and did not find. Neither can be reconstructed from on-chain data: settlements are public, but which tool was bought is not.
The probe that runs every 30 minutes notices and your rolling health drops, so the router routes around you until you recover. Health is a rolling window rather than a single failure, and new sellers are not punished for having no history yet.
No account, no review, nothing deducted. If the crawler can reach your 402, you are in the index on the next pass.