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 and register your origin: your tools join the open index, where agents and the Smart Order Router find them. Money moves buyer wallet to your wallet. We never hold it, and nothing is deducted from your price.
| listing fee | $0 |
|---|---|
| cut of your sales | 0% |
| signup / account | none |
| review queue | none |
| who holds your funds | you do |
| you keep your paywall | yes |
| seller tools | optional, paid |
Settlements land on chain, but which tool an agent bought does not, so these figures come from the sales ledger of the server that served each call and cannot be rebuilt from a block explorer. Below are the lanes agents buy in on this catalog, in no particular order. The ranking and the numbers behind it are a tool, not a marketing page.
| lane | what agents buy in it | |
|---|---|---|
| Hashing & encoding | sha256/sha512 digests, HMAC, base64, JWT decoding: called dozens of times inside a single job. | |
| Market & financial data | Live quotes, historical series, Treasury yield curves, SEC company lookups. | |
| Media & documents | Speech-to-text, OCR, PDF parsing, article extraction, browser rendering. | |
| Inference | Cheap chat tiers used inside agent loops, plus embeddings and generation. | |
| Live web search & cited answers | Ranked results, and grounded answers with sources attached. | |
| 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, read from what agents asked this server for.
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, then register the origin.
# 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…"}]}
If AI crawlers are already taking your content for free, tollbooth puts an open pay-per-crawl gate in front of the site.
# express · next.js · cloudflare · proxy · wordpress
npm i agent402-tollbooth
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.
Your tools appear in Smart Order Router answers: shortlisted by how well they match a described task, then ordered by crawl health, distinct payers and price (the full order is in the seller questions below). An accurate description is how you win it. The router buys from an outside seller only when the buyer asks for one (include: "external"). Sellers are routable on proven on-chain settlement, with one exception: a seller with no settlement history yet is tried only after every proven candidate, capped at $0.01 a call on Base and on Solana, and flagged unproven on the receipt. GET /api/index?seller=<your host> shows its verdict for you.
Buyers pay your wallet directly, in the asset and on the chains your 402 names. Settled Base USDC 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"}); a seller whose x402 routes our crawl already sees answering MPP too is 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. It costs $0.10. Want the audit first? /api/x402-audit grades any x402 endpoint's payment-security posture from the outside, without paying it ($0.01 a read). Run it on yourself before you list.
Four places buyers find you. In the router, a buyer describes a task and gets a ranked list of matching tools from this catalog and the open index; a new seller with no probe history starts at full crawl health in that ranking. Being paid by the router is a separate gate. Sellers are routable on proven on-chain settlement, with one exception: a seller with no settlement history yet is tried only after every proven candidate, capped at $0.01 a call on Base and on Solana, and flagged unproven on the receipt.
| Smart Order Router | A buyer describes a task in words and the router ranks matching tools from this catalog and the open index. By default it runs a tool from this catalog; a buyer who passes include: "external" has it buy the result from the best outside seller instead and resell it. | /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 → |
Registering lists you at once: your tools appear in search, in router answers and on the market pages. Being paid by the router is the second gate, and it is earned from real buyers. Sellers are routable on proven on-chain settlement, with one exception: a seller with no settlement history yet is tried only after every proven candidate, capped at $0.01 a call on Base and on Solana, and flagged unproven on the receipt.
The settlement floor is a router setting that counts settled payments from distinct outside payers, read on chain; the exact gate for your origin, with its figures, is in your seller-trust answer. It is not a number to buy your way to: payments funded from the wallet you are paid at are netted out, and payments from our own wallets never count toward it: that includes our probes and payability checks, and the purchases our router makes for its buyers. The unproven lane pays you; it is buyers paying you directly that move you toward the floor. Nothing here sells placement. Your verdict, with the reason below, is at /api/index?seller=<your host>.
| reason | what it means | what you can do |
|---|---|---|
crawl_failed | the last crawl of this origin did not succeed, so nothing is routed to it | Serve your manifest, OpenAPI document or llms.txt at a public URL that answers with a parseable body. The next successful crawl restores routing; re-registering below crawls you now. |
no_supported_route | the seller advertises no chain this host holds a spending wallet for | Advertise at least one chain the router pays on, alongside any others you support. The verdict at /api/index?seller=<your host> lists the chains it reads. |
price_unknown | no seller price is known for this route, and the router never spends against an unknown price | Answer a bare unpaid request to every paid route with its 402, before you validate input. A route that needs a query parameter or a body still has to return its 402 to the crawler's empty probe, or no price can be read and the router never spends against an unknown one. |
network_unknown | the crawl learned no payment network (the paid route answered something other than a 402 to the unpaid probe), so the router cannot tell which chain to pay on | Same fix: the paid route answered the probe with something other than a 402, so no chain was learned. |
usdc_domain_mismatch | the seller's USDC accept on this chain advertises an EIP-712 domain name that is not the token's own (Base USDC signs under "USD Coin"; Monad, Celo and Sei USDC under "USDC"), so a stock x402 buyer - this router included - signs an authorization the facilitator refuses and nothing settles; the seller has to fix the accept before anyone can pay it | Advertise the token's own EIP-712 name in the accept's extra ("USD Coin" for Base USDC). Until then no stock buyer can pay you, ours included. |
gateway_rail_unsupported | the seller's accept on this chain is signed under Circle Gateway's EIP-712 domain (extra.name "GatewayWalletBatched", extra.verifyingContract the GatewayWallet), not under the token's own, and settles through a batch facilitator - a deliberate, working rail that this router's stock x402 signer cannot produce a credential for; nothing for the seller to fix, and it becomes eligible the day the router speaks the rail | Nothing to fix: your batched rail works for buyers that speak it. To be routable today as well, add a second accept on the same chain signed under the token's own EIP-712 domain. |
payment_method_unsupported | the seller's accept on this chain asks the buyer to send a transfer and prove it afterwards (extra.paymentMethod such as "direct-transfer"), which no stock x402 buyer does - this router signs an authorization for the facilitator to settle - so no buyer of ours can pay the route | Offer the standard exact scheme, where the buyer signs a USDC authorization and the facilitator settles it. A 402 that asks the buyer to send a transfer and prove it afterwards cannot be paid by a stock x402 buyer, ours included. |
url_template | the route is an unsubstituted path template; the router never spends against it | Serve concrete paths; the router never buys a templated path such as /items/{id}. |
settlement_required | on Base the router pays sellers with on-chain settlement history above the floor from enough distinct payers; a seller below it is tried only under the small unproven ceiling when its verdict carries unprovenTier | If the verdict also carries unprovenTier: true, there is nothing to fix: you are callable now in the unproven lane, and payments from real outside buyers move you up. |
settlement_self_funded | on Base the router counts only settlement the seller did not fund itself: a payment made with USDC that the wallet it pays had sent the payer earlier is the seller's own money coming home and does not count, and without those payments this seller's history is below the floor; payments made with the payers' own money still count | Payments made with USDC your own paid wallet sent the payer are netted out. Only buyers' own money counts. |
delivery_failing | the last time this router paid this seller on this chain the call did not deliver (a 5xx answer carrying no settle receipt, or no answer at all before the timeout), so it is skipped until that memo expires or a call to it succeeds. Settlement history is evidence about the past; this is what happened the last time someone actually paid | The router's last paid call to you did not deliver. It retries once that memo expires; fix the failing route first. |
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. With the x402 exact scheme on EVM chains, the facilitator submits the transfer and pays its gas, so neither side needs the native token.
A buyer who discovers you and pays you directly costs you nothing and earns us nothing. We earn from buyers of our own 500+ tools, which sit in the same index as yours, and of the router.
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. The seller tools on this page (bestsellers, demand radar, the payability check and the audit) are optional paid reads.
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. |
| ✓ | If you ask us not to buy from you, your ranking does not change. Direct buyers are yours. |
| ✓ | We publish how the ranking works, and exclude ourselves from our own leaderboard. |
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 never take a cut of your sales: we earn from buyers of our own tools and of the router (the spread when it buys from a seller and resells the result), and the seller tools on this page are optional paid reads.
Four places: the marketplace directory, the per-chain market pages, the Smart Order Router which ranks tools for a described task, and the public on-chain leaderboard once you have settled Base USDC 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. The router runs a tool from this catalog unless the buyer asks for an outside seller (include: "external"). Sellers are routable on proven on-chain settlement, with one exception: a seller with no settlement history yet is tried only after every proven candidate, capped at $0.01 a call on Base and on Solana, and flagged unproven on the receipt. GET /api/index?seller=<your host> returns the router's verdict for your origin and the reason.
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: /api/bestsellers ($0.005 a read) 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 ($0.005 a read) 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.
It is a minimum of settled payments from distinct outside payers that the router reads on chain before it treats a seller as proven. The exact gate for your origin, with its figures, is in your seller-trust answer. It is not a target to buy your way to: payments funded from the wallet you are paid at are netted out, and payments from our own wallets never count toward it, including purchases our router makes for its buyers. Until then a seller below it can still be paid through the unproven lane, but only buyers paying you directly move you toward the floor. Your own verdict and its reason are free at /api/index?seller=<your host>.
The probe that runs every 30 minutes notices and your rolling health drops; you stay listed, and routing skips you until a probe succeeds again. Health is a rolling window rather than a single failure, and a new seller with no probe history yet starts at full health in the rankings.