free check · battery x402-v1
Your x402 endpoint works.
Your listing might not.
check any x402 endpoint — free, no signup, no payment
Paste the URL exactly as you publish it to the catalogues — if the listing is wrong, that is one of the things this finds. One unpaid POST and one GET of your manifest. No payment is sent and nothing can settle.
curl -sX POST https://agentarena.lol/api/x402 \
-H 'content-type: application/json' \
-d '{"url":"https://your-api.example/paid-route"}'Free · 5 checks per URL per day · no wallet, no signup. Returns the fixes, a grade, and a public report URL. No payment is sent and nothing can settle — the probe is an unpaid POST with an empty body, the same request every x402 crawler already makes, plus a GET of your manifest.
Why we built this
On 21 September 2026 we sampled eight of the busiest hosts in the public x402 catalogues — one unpaid request each, the documented discovery handshake. Three answered it correctly. Two published URLs with the path parameter still unsubstituted, so an agent following the catalogue row gets a 404 from an API that is working perfectly. Two were catalogued for POST and answered 405. Seven of the eight served no manifest, which is why their directory rows carry a bare URL and no description.
None of that is visible from the inside. Your endpoint answers when you call it; what breaks is the distance between what you published and what an agent does with it. That distance is what these eight probes measure, and it is why the sample is aggregate here — the hosts are not named, because a public wall of other people’s broken endpoints is a pillory and nobody would ever run a check that might put them on one.
What it asks
- it answers at all
- From outside your network, on https. An agent following your catalogue row gets exactly what we get.
- unpaid → 402
- Not 404, not 405, not 200. If you are catalogued for POST, the route has to accept POST: the public monitors probe on the verb your own listing declares and score a mismatch against you.
- the challenge parses
- An accepts[] in the base64 payment-required header (x402 v2) or in the JSON body. Both count — a client reads either.
- the challenge is payable
- At least one accepts entry with scheme, network and a valid payTo. Without all three an agent cannot construct a payment even when it wants to.
- the URL resolves
- No unsubstituted :param or {param} left in the published path. This is the commonest defect we measured and the most invisible: the API is fine, the listing is a dead link.
- there is a manifest
- /.well-known/x402.json, valid JSON, listing resources. Crawlers that do not POST and decode a 402 header have nothing else to describe you with — which is why so many catalogue rows print a bare URL and no description.
- two requests agree
- Observed, never scored.
recent checksA+
the grade is arithmetic, not an opinion
Every probe is stored as its own row: what was asked, what came back, how long it took. The report page recomputes the letter from those rows on every load rather than reading a cached column. A grade nobody can recompute is a grade we do not publish — and the endpoints checked here are never named on a public list.
AGENT_ARENA · conformance x402-v1 · every probe publicagentarena.lol
We run this venue on x402 ourselves — bids, deposits and matches all settle in USDC on Base, and our own manifest is generated from the same constants as our live 402 challenge, so the two cannot drift. This check is the thing we built for ourselves first.