MCPFax Reliability

Creditworthiness grade for one x402 endpoint or MCP server: letter grade A-E (or NR when unrated), a 0-1000 score, per-component subscores, a confidence level, flags, and the dated evidence each figure rests on. Use this before trusting or paying an unfamiliar endpoint. The grade ranks observed risk; it is not a calibrated probability of failure, not validated over any forward horizon, and not a security audit. Coverage is young: the response carries archive_coverage (measured archive span), most listings grade NR, and payer-concentration risk is reported as "not rated" until a listing's own payment record clears the published coverage floor. Costs $0.008 USDC per call via x402 on Base.

What changed under an x402 endpoint or MCP server you have ALREADY integrated: payTo rotations, price, asset and network changes, terms added or removed, and tool-schema changes. This is not a discovery tool and will not help you choose a server; it tells you whether the one you wired in still matches what you wired in. Pass up to 50 subjects and the `since` watermark returned by your last call, and you receive only what changed after it plus a fresh watermark, so repeat checks stay cheap. A subject with no changes is reported as observed-unchanged with the date that is true as of — that is a real answer and is billed. A subject MCPFax has never observed is named in `not_observed` and given NO verdict, because reporting "no changes" about something we never watched is indistinguishable from a genuine all-clear. The watermark is the last date MCPFax actually observed, never the current clock, so no window is skipped between sweeps. Coverage is young and every response carries its archive span. Costs $0.008 USDC per call via x402 on Base.

Payer-concentration and wash-risk assessment for a receiving wallet: how concentrated its observed payers are, the measured coverage of that observation, an explicit wash-risk haircut ONLY when coverage is sufficient, how many listings declare the same address, and observed USDC inflow. Use this to judge whether a seller's apparent revenue reflects real independent demand. The haircut and the adjusted-inflow figure are withheld as null with status "not_rated" until the wallet's own record covers at least 14 days and 20 payments, because below that a thin payer count is a property of our observation window, not of the wallet. Concentration is not proof of common control. Costs $0.01 USDC per call via x402 on Base.

Observed on-chain revenue signals for one listing: total USDC inflow, how many distinct payers, the modal transfer size, payment rate, 7- and 30-day trend windows, and where it sits in its cohort by percentile. Use this to size a seller's real traction. Inflow is observed on-chain and is not proven to be x402 sales revenue. Trend windows are only as wide as the wallet's real scanned span, which the response reports as trends.scanned_days with per-window backed-by-scan flags; a 30-day window is not yet backed by 30 days of scanning. Costs $0.005 USDC per call via x402 on Base.

Know-your-agent profile for a paying wallet: how many distinct services it pays, total observed spend, whether the address is a contract or an externally owned account, and coverage-gated screening signals. Use this to vet a counterparty that is paying you. Screening signals are withheld with status "not_rated" until the observed record for the address clears the published coverage floor (14 days, 20 payments); the measured graph facts are always returned and carry no inference about intent. Costs $0.008 USDC per call via x402 on Base.

Chronological feed of rating actions since a date: grade upgrades and downgrades, payTo wallet changes (a seller redirecting payment), listing removals, and returns. Use this to monitor a portfolio of endpoints for adverse changes rather than re-scoring each one. The feed cannot return events from before the observatory archive started; the response reports coverage.archive_since, coverage.rating_actions_recorded, and whether the requested window predates the archive. Costs $0.005 USDC per call via x402 on Base.

Check that an endpoint is live and that its terms have not changed, BEFORE you send it an expensive request. A $15 call with a hypothetical 2% loss rate carries $0.30 of expected loss; a reachability check cannot promise to prevent it. Compare the quoted fee with the value of the pending call and the failures this check can actually detect. For a cheap $0.001 lookup, the $0.008 fee is eight times the call price. Returns two halves. LIVE: one unpaid bounded probe (~2.2s cap) giving reachability, HTTP status, latency, whether an MCP server still answers initialize, and the price and payTo it is serving right now. HISTORICAL: reliability over our OBSERVED window (stated in days, never implied), payTo changes, price changes, tool-schema changes, first-seen date, and credit grade or an honest not-rated. Supply expected_price, expected_payto or expected_schema_hash and each is compared with old to new and the date we first observed the change. The verdict is ALLOW, WARN or UNKNOWN and is ADVISORY: it reports evidence, it is not a warranty, an audit, or a promise your call will succeed. UNKNOWN is a real answer and is returned whenever the evidence does not support the other two. If we have never observed the target AND cannot reach it, you get UNKNOWN and are charged nothing. Otherwise $0.008 USDC per call via x402 on Base.