FactStamp

Paid verification for agents, and a public record of every paid answer. Each call returns a cited, dated finding with a signed receipt you can verify offline, without asking us. Each settled call is written into a public log, and each day's root is stamped onto the Base blockchain whenever that day held a payment from someone other than us. When a check has to stay confidential there is a private option: a flat US$25 on top of the call price seals the request, so the world can see that a call happened and prove it later, but never learn what was asked. No model sits in the verdict path, and unknown is a first-class answer.

Live service: https://agents.factstamp.dev

What this repository is

The published machine interface of the FactStamp service, mirrored here so it can be read, diffed and cited without a wallet. Each row names the live route the copy came from, so any file here can be checked against the service in one request:

These are dated snapshots, not a live feed. Coverage and prices move as registers change, so a copy here can lag the service. When the two disagree, the live route wins — fetch it and believe that, not this. The files exist so a person or an agent without a wallet can read the interface, and so a reader can cite exactly what was published on a given day.

The service's private source is not published here.

Routes

Paid routes include /citation, /package, /check, /entity, /entity-file, /bulk, /document, /watch, /watch/portfolio, and /verify for receipt checking. Prices are published, per call, in the files above rather than in prose here.

Published prices at the time of writing

Taken from /health and /llms.txt as served:

• figure door — US$0.05
• entity door — US$0.10 to US$0.25, set by the depth of the country you ask about: US$0.10 for a country publishing 1–4 verifiable items, US$0.15 for 5–6, US$0.20 for 7–9, US$0.25 for Australia's fifteen. The quote is shown in the payment challenge, before any money moves, and a country whose register cannot answer today is not sold at all — it is refused with no price rather than charged for an "I don't know".
• entity file — US$0.438119 (33p in the UK, at the dated rate carried on the answer and the receipt)
• citation — US$0.02, package lookup — US$0.02
• standing work: watch US$0.50, whole document in one call US$0.25, bulk at a flat US$0.12
• company packages: US$2.00 and US$10.00, one-time, from the human page at /company

If a number here ever disagrees with llms.txt or openapi.json as served, the served file wins.

Receipts

Every paid answer carries a receipt signed with Ed25519 over the exact findings and the file's hash, so a third party can verify it offline against the published issuer and key document — no call back to us, and no trust in our uptime. The key document at /.well-known/factstamp-issuer.json states exactly which bytes the key identifier is derived from and carries a worked example, so the derivation can be reproduced in any hash tool. A receipt proves that FactStamp said this, on this date. It does not prove that the register itself is right, and nothing in this service claims it does.

The public record: the ledger, and what is stamped on Base

Every settled paid call, over HTTP and over MCP alike, appends one entry to a public log. The log is an RFC 6962 Merkle tree; each UTC day's log reduces to a single root, published at /ledger/root along with the last thirty days.

A day's root is written to the Base blockchain — one small data-only transaction, magic 0x46535401 followed by the 32-byte root — only when that day held at least one settlement paid by someone other than us. Our own test payments never anchor a day. The rule exists so that an anchor means something: a day is stamped because a stranger paid, not because we were busy.

Days already written (verifiable on Base, chain id 8453):

A day that held no outside payment is published with the verdict that says so, rather than being quietly left blank. The honest limit: an anchor proves the root was committed publicly on the day the transaction landed, not on the day of the payment — the payment itself is already a public record, because it is a transfer on the same chain. The anchor adds our side of the story: that the answers we gave were fixed before anyone asked to see them.

Private requests: the sealed-entry option

By default a paid call's entry is published in full — the door, the price, the verdict, and the fact that the call happened. For a caller who needs the call itself to stay confidential there is a zero_knowledge option, declared on the request.

• Price: US$25.00 in addition to the call's own price. A US$0.10 entity check declared private costs US$25.10. The payment challenge quotes the total before anything is paid.
• What is published: an entry_id, the day, the price, the scheme (salted_commitment_v1) and the network. Nothing else.
• What is sealed: the question, the answer and the verdict. The entry is committed to with a salted hash, so its existence and its position in the log are public while its contents are not.
• What that buys: you can prove later that a specific call happened on a specific day — by revealing the salt to whoever needs it — without ever having published what you asked.

The private option is documented at /ledger/zero-knowledge, with its own root at /ledger/zero-knowledge/root and its entries at /ledger/zero-knowledge/entry/{entry_id}. It is an option on the paid doors, not a separate service.

What this service is not

• Not a KYB provider, and not a substitute for one. It does not perform customer due diligence on anyone's behalf.
• Not complete by assertion. Any register we did not consult is named on the answer as not consulted. A register we could not read returns unknown, never not found.
• Not a fetcher of records you can already get at no cost. You are paying for the citation, the check and the receipt, not for the register's own data.

Issues

Corrections about a claim we make are welcome as issues here. If we have said something about a company, a number or a register that is wrong, that is the fastest way to tell us.