The short answer
Every Zambo call issues a receipt in the AER-1 format, specified by the IETF Internet-Draft draft-zambo-aer1-26, with a public conformance corpus of 126 vectors and 129 checks under kit v1.5.7. The receipt lives at its own public link, zambo.dev/run/ plus the receipt ID, and the verifier at zambo.dev/verify checks any of them for free.
Scope, stated once: an agent receipt is a record of one ai agent tool call that anyone can check: it keeps the exact saved bytes and their sha-256 digest, and it proves the result was not changed since it was saved, not that it was right.
That scope is why the tool can be free and simple. It does one narrow, fully mechanical thing: recompute and compare. There is no opinion in it to sell.
The check, step by step
- Get the receipt link. Anyone who ran work through Zambo can hand you the link, and every receipt on the public stream at the live receipt stream is checkable the same way.
- Paste it at zambo.dev/verify. The full link or just the receipt ID both work.
- Read the result. Verified means the digest recomputed from the saved bytes matches the digest recorded at call time. Anything else means the record in front of you is not the record the call produced, and the claim resting on it should not be accepted as shown.
- Then judge the content. Verification settles that the record is intact. Whether the work itself was good is your review, now aimed at the real output instead of a copy of it.
Worked example: one free check, run before this page shipped
From the public stream on October 25, 2026: a capability_search call saved at 2026-10-25T17:19:06Z, receipt at zambo.dev/run/01318325-ac85-4038-8797-c426df2f3e29, saved result digest sha256:7709ab1980a60850bcbffa17d48fc3f73885afabe1a84858c4937f88903b113e.
The verification endpoint returned verified for this receipt, with the recomputed digest matching the saved digest. Run the same check yourself at zambo.dev/verify: it takes the link, costs nothing, and needs no account. That reproducibility is the entire offer. You do not have to trust this page, the agent, or Zambo. You have to run one free check.
Why verification is free, and what is not
| Action | Cost | Account needed? |
|---|---|---|
| Verify any receipt at zambo.dev/verify | Free | No |
| Open any public receipt at zambo.dev/run/{id} | Free | No |
| Run your own calls and get receipts | 20 free calls per day to start | No, to start |
| A heavy day of full access | Day Pass, $0.99 USDC on Base for 24 hours | At checkout |
| Ongoing access | Zambo Pass, $29 for 30 days, one payment | At checkout |
The split is deliberate. Checking stays free forever, because the value of a receipt collapses if checking it sits behind a paywall. Running the work is what the Pass pays for: one MCP endpoint at https://zambo.dev/mcp, 153 tools total, 35 on the default surface, a receipt on every call.
Start getting receipts on your own work
Add Zambo to the AI you already use at zambo.dev/add. Your agent's calls start issuing receipts immediately, 20 free calls per day, and every receipt you produce can be checked by anyone you hand it to, free, at the same verifier. The free check is also the sales pitch: once a client or a teammate has verified one of your receipts themselves, the next handover you send needs no persuading.
Questions, answered
Is it really free to verify an AI agent receipt?
Yes. The verifier at zambo.dev/verify is free, with no account and no signup. Paste a receipt link or a receipt ID and the check runs in front of you. Verification stays free because a check that costs money or needs permission would not be a check anyone actually runs.
What does the verifier actually check?
It recomputes the sha-256 digest of the exact saved bytes on the receipt and compares it with the digest recorded when the call ran. A match returns verified and proves the saved result was not changed since it was saved. A mismatch means the record in front of you is not the record the call produced.
Does verified mean the agent's answer was right?
No. Verified means the saved result was not changed since it was saved, not that it was right. Judging the content still takes review. The verifier's job is narrower and fully checkable: the thing you are judging is the thing the agent actually produced.
What does it cost to start getting receipts on my own work?
Nothing to start. Add Zambo to your AI and you get 20 free calls per day, each with its own receipt. A Day Pass is $0.99 USDC on Base for 24 hours of full access, and the Zambo Pass is $29 for 30 days, one payment.