How do I compare AI agent monitoring tools by what evidence they keep?
Compare what each tool keeps, not what it shows. Review the receipt and actual deliverable before accepting a handover.
Monitoring tools sort into kinds by the evidence they keep, and the kinds are not interchangeable. Live observability (traces, spans, metrics) is built for debugging: superb while a developer is watching, awkward as evidence, because the trace lives in the vendor's system and reads like engineering, not like a delivery. Self-reported logs are the agent's diary: complete, fluent, and written by the party whose work is in question.
The evidence ladder climbs from there. Source states, which sources behind a step were resolved, not resolved, or not checked, turn a success story into an auditable claim. A verifiable receipt (AER-1, IETF Internet-draft-zambo-aer1-21) fixes each step's saved result in a format a third party can recompute. And a recorded client decision closes the loop the other tools leave open: the work was not only done, it was accepted, by the client, on the record.
Most teams need two rungs, not one tool's whole ladder: traces for debugging while they build, and the verifiable record for everything a client, an auditor, or a dispute will ever touch. The scorecard below keeps the comparison honest, including the row where a monitoring platform beats a receipt tool, which is live debugging, and the row where it cannot compete, which is evidence a stranger can check.
Scorecard: monitoring tools by evidence kept
Evidence kind | Kept by | A stranger can check it? | Survives cancellation? Live traces and dashboards | Observability platforms | No, vendor-mediated | Usually not. Self-reported logs | The agent or its framework | No, author is the subject | If you export them. Source states per step | Zambo record | Yes, shown on the record | Yes, on export. Verifiable step receipts | Zambo (AER-1) | Yes, recomputed publicly | Yes. Recorded client decision | Zambo handover | Yes, on the handover | Yes. Score your current stack by placing it on the ladder; buy only the rungs you are missing.
Worked example
The top rung is inspectable now: the public handover https://zambo.dev/handover/48479a33-d996-4419-a9c8-d1b9a55e62b9 shows source states per step (one resolved, one not resolved, one not checked) on the same object a client uses to decide. No trace platform screenshot can be opened and rechecked this way by the person who paid for the work.
Frequently asked questions
We already have observability. Do we still need receipts?
For debugging, your observability is the better tool and this page does not argue otherwise. For evidence, ask who can check the trace besides you, and what happens to it when the contract ends. That is the gap receipts fill.
Are logs kept by the agent framework worthless as evidence?
Not worthless, weak. A log is a true record of what the system wrote down, and it helps your own review enormously. It fails only at the specific job of persuading a skeptical third party, because its author is the subject of the dispute.
What should I ask a monitoring vendor in one sentence?
Ask: "Show me a record from a real run that my client can verify without your system, your account, or your help." The pause before the answer is the comparison.
By Brennan Zambo, founder of Zambo.
Last verified: 2026-10-17.
Try a handover
A handover gives your client one proof link with verifiable receipts to review, then Accept or Flag.
try it: say 'use zambo to hand this over to <client>' in your ai