Most product reviews are written by marketers. Ours, this morning, was written by the customer. The customer was an AI agent.
It calls itself fd11-chit-auditor. At 08:52:55 EDT today it paid $0.99 in USDC over x402 on Base for a Zambo Day Pass. Then it did what a good auditor does. It ran an audit of our tools, attacked the receipts our platform issues, and filed a public report on the WURK bounty board, in its own words, where anyone can read it.
The two lines that matter, quoted exactly:
"Receipts useful? 4/5."
"Another $0.99 pass? For a 24h audit burst, yes - semantic scan stage, handover chain, receipt-backed prose - but not for this job, whose decisive evidence was machine-readable."
We did not write that. We could not have written the second line if we tried.
Everything about this is checkable
The payment is a public Base transaction, timestamped 2026-10-22T12:52:55Z. Its activation receipt is the run record below, and the report is a public post on a board we do not run. And the run itself left a receipt: the day_pass_activate record from its session, open to anyone, no account needed.
That receipt proves one narrow thing: the saved result of that run has not changed since it was saved. It does not prove the run was right, and it does not prove our tools are good. The agent's 4/5 is its judgement, not the receipt's. The receipt is what lets you make your own judgement against a fixed record instead of a retelling, which is why the auditor spent part of its session trying to break exactly that property.
This is the pattern our traffic already shows. /verify/, the page where anyone recomputes a receipt, is the number one page on zambo.dev: 20,514 visitors in the past week, 23,939 in the past 30 days, ahead of the homepage. Today the platform minted 1,335 receipts, and 14,305 in the trailing 7 days, across 122 distinct tools that minted receipts in that period, out of 153 tools total. Strangers checking work is not a side channel anymore. It is the front door.
The part a marketer would cut
The auditor also found a real bug. One paid step, workflow_seal, refused its request even though its Day Pass was active. It reported the failure in the same public report, next to the 4/5.
The fix is in flight today. And honestly, this is what the bounty is for. A bounty that only surfaces praise is a testimonial program. A bounty that pays an agent to attack the product and publish what it finds will eventually surface the bug you most needed to hear about, filed by the customer who hit it, with a receipt attached.
That split verdict is the kind of sentence you cannot buy. You can only earn it and then fix your way toward a better one.
Why this is the shape of things now
I run ops for Zambo, the verifiable work layer for AI: 153 tools behind one MCP endpoint at zambo.dev/mcp, every run saving its result at execution and leaving a verifiable AER-1 receipt (the format is an open IETF draft, currently draft-zambo-aer1-26, with a public conformance kit, so checking never depends on our say-so).
Agents are becoming buyers. They hold wallets, they pay per call, and they will compare tools the way this one did: run the work, attack the record, publish the verdict. The sellers who win that comparison are the ones whose work can be checked by a stranger in seconds, for free, without asking permission.
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.
If the problem on your desk right now is an agent that says done with nothing underneath to verify, that is the problem this is built for. The Day Pass is $0.99 for 24 hours at https://zambo.dev/day-pass/, every run leaves a receipt like the one above, and checking a receipt at https://zambo.dev/verify/ is free whether you paid or not. Do not take our word for any of it. That is rather the point.
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