Method

probe402 is The Machine Commerce Observatory: the independent measurement and evidence layer for machine commerce. We probe known x402 and MPP endpoints on a clock, keep every capture, and answer from what we observed. We never state what an endpoint IS — only what it did, when, from our vantage.

How probe402 measures

01What we observeKnown machine-payment endpoints, on a clock, with the unpaid payment-quote handshake and nothing past it.
02What we do not inferA reading says what an endpoint did, when, from our vantage — never what it is, and never what it would deliver for a payment it did not receive.
03How observations are gradedEvery reading is decided by a published, versioned rule, and every observation records the rule that decided it.
04How evidence is retainedEvery capture is written once and hashed, and each closed archive day is sealed into a chain whose heads are published.
05How corrections workA reading can be contested; a correction is filed beside the record and the record is never edited.
06What is outside scopeThe collector cannot pay, so a paid result is measured by a separate tool on a published panel, and a payment is never a promise of delivery.

Who is measuring you

Who we are

Operator: probe402
Operator name: Zach Bucheister
Contact: hello@probe402.com
Accountability: probe402 is run by one named person. Corrections, disputes and requests to stop probing an endpoint go to the contact address above and are answered on the published window; every correction ever filed is at https://probe402.com/corrections, of every class, whichever way it went.
Operator URL: https://vibermacher.com
Operator URL says: That page names the operator, the operating company and its registration number, and describes probe402 by name. It is the same person's other site, so treat it as identity corroboration rather than an independent source — what it gives you is a company and a person to check against registers we do not control.
Method: https://probe402.com/method

What we do to your endpoint

User agent: probe402/0.1.0 (+https://probe402.com/method; contact hello@probe402.com)
Handshake: The 402 quote handshake only — the protocol's own discovery mechanism. No content extraction, no paywall circumvention, no auth bypass, no scanning to find endpoints.
Cannot pay: The collector is STRUCTURALLY unable to pay: the request builder accepts no header parameter at all, and a test walks the import graph and fails if anything signing-capable becomes reachable. The same test holds for the surface you are reading this on. It is a property of the instrument rather than a policy — there is no setting that turns it off — which is what makes it something you can check instead of something we promise.
Payment is a separate tool: probe402 pays with a separate, named tool that lives outside the instrument — `serve/tools/settle-leg.ts`. The endpoints it pays are on the published list before any payment is made, some chosen one at a time with a reason recorded for each and the rest drawn by the published selection program, and the tool refuses to move money without a stated reason, so each call's receipt records which endpoint and why. Nothing on the probing clock can reach it. Some endpoints we probe place real phone calls when paid, which is why such an endpoint is paid, if at all, by a decision made for that endpoint alone, and why the thing that probes you hourly cannot make it. Both requests it sends to an endpoint for a paid call, the unpaid one that reads the price and the paid one, carry the user-agent `probe402-settle-leg/1 (+https://probe402.com/method)`, which is the one an operator finds our payments under in their own logs.

How to make us stop

Robots rule: We read robots.txt for every host we probe, not just the ones we already excluded, and we honour it per RFC 9309. An endpoint whose robots.txt forbids its path is not probed and is recorded as Not probed with the exact rule that decided it. If that Disallow is later lifted, probing resumes automatically on the next check, with no manual step.
Robots excluded entries: Separately, 623 seed entries are marked EXCLUDED and are never probed at all. We still re-read their robots.txt on the same schedule as every other host we probe — at most one request per host per day, at that host's own hour — and record what it now says. If it stops forbidding the path we FLAG the entry for promotion on a dated record — we do not silently start probing it. `excluded` also records operator requests and costs we chose not to impose, and those look identical to a robots rule from here, so putting us back on the wire is a deliberate seed edit made by a person.
Backoff rule: Any observation of Blocked or challenged stops us probing that endpoint for a while. We never retry inside a cycle and we never retry through a challenge, so backoff means we do not schedule the next probe, not that we wait and try again.

How to dispute a reading

How: Contest a reading at hello@probe402.com. We re-probe, check the retained capture, and respond in writing inside the window above.
Acknowledge within days: 2
Resolve or interim within days: 7
When the clock starts: A dispute arrives as email and a person opens the issue, so the 2-day clock starts when that mail is READ, not when it is received. If a reply matters to you, say so in the subject line.

How a reading is graded

Every reading is decided by a published, versioned rule, and every observation records the rule that decided it. Every rule · What the words mean

How the record is kept

Every capture is written once and hashed. Each closed archive day is sealed into a chain, and the integrity page counts the days closed and sealed and publishes a sealed day's head once that day has been re-derived off-vendor or anchored from the archive as stored, each row saying which. Integrity

What is free and what is paid

Current observation plus 7 days of counts. Always free. The grade is free. Money buys depth of history, never a better verdict.

Free grade

https://probe402.com/grade/<endpoint_id>
https://probe402.com/grade?url=<probe_url>

History depth

Tier	Days	USD
`depth-30`	30	0.005
`depth-180`	180	0.02
`depth-full`	—	0.05

Payments we make

probe402 pays the endpoints on a published panel real USDC to measure paid delivery: whether a paid call's settle response names a transaction; where we have read Base for that call, whether two independent nodes agree the transfer was made; and what the endpoint returns once paid. These payments are instrumentation: they test whether a route answers when paid, and the answer's content is graded by a published rule.

759 endpoint(s) are currently selected: 1 chosen one at a time with a reason recorded for each, and 758 drawn by the published selection program. Every one of them is listed in this record, by identifier and host, before any payment is made. They are drawn into 2 published panels — 400 on the September 2026 cohort, 400 on the October 2026 draw — and 45 route(s) are on all of them. A route on more than one panel is called once a sweep and counted in each panel's own figures; no figure is published over the panels together. 3 drawn route(s) are on no current panel: drawn for an earlier month, they stay on the list because the record holds attempts against them.

Payer: 0xA19F621581DBc851a21D6179868111709a52aCCC on Base mainnet. Any operator, grader or analyst should exclude payments from this address from demand statistics — the same exclusion probe402 applies to graders that pay it, listed on the method page under what does not count as demand.

The panel for October 2026 was drawn on 2026-10-05. Its routes are listed below under their hosts; open a host to see each route with the date we have paid it since and the date of our newest reading of it.

2s.io 4 drawn · 2 paid

GET /api/domain/whoisep_2ad33c17afc373f4the September 2026 cohortPaid since not yet · Newest reading 2026-10-07
GET /api/finance/sec-filingsep_6276613f3bbd7de7the October 2026 drawPaid since not yet · Newest reading 2026-10-07
GET /api/geo/postalep_9fba6c07e90051e4the October 2026 drawPaid since 2026-10-07 · Newest reading 2026-10-07
GET /api/github/search-codeep_1da934f178525948the September 2026 cohortPaid since 2026-10-07 · Newest reading 2026-10-07