---
title: "Verifier: definition | KYA glossary"
url: https://knowyouragent.ch/en/knowledge/glossary/verifier
lang: en
updated: 2026-10-12
license: © Innopulse Consulting GmbH
---

# Verifier

A verifier is the point in a flow where an agent action is checked against the mandate before execution, for example a gateway in front of a tool.

In access-control terminology the verifier corresponds to a policy enforcement point. It produces the decision and only lets the action through if it is allowed. KYA, by contrast, is a public verifier in the second sense: it verifies the receipts afterwards.

## Example

A shop adds two verifiers: before accepting an order it checks the mandate, after delivery the receipt. Both create a certificate that can be recomputed later.

## How it differs

A verifier is a place in the flow; the [verifying party](https://knowyouragent.ch/en/knowledge/glossary/verifying-party) is the responsible organization. knowyouragent.ch is a public verifier that any verifying party can use.

## In practice

- Place the first verifier before the action, not after. Checking before execution prevents damage; checking afterwards only proves it.
- Add a second verifier after execution that checks the receipt against the decision. This reveals deviations between permission and execution.
- At every verifier, log the certificate with its reportDigest, so every decision can be recomputed unchanged later.

## Role in KYA

As a neutral verifier, KYA checks evidence from different vendors by the same rules. Verification runs locally in the browser or through the engine in one's own system.

A term from the flow, not a check of its own. [To the method](https://knowyouragent.ch/en/method)

[Verify now: open a matching example](https://knowyouragent.ch/en/verify?beispiel=paket)

## Frequently asked questions

### What is a verifier?

The place in the flow where evidence is checked, for example before accepting an order or before a payment.

### What makes KYA a neutral verifier?

KYA issues no evidence itself and checks all formats by the same open rules with public test vectors.

### Where are verifiers used?

Wherever an agent's action has consequences: before payments, orders, bookings and submissions to authorities.

### Does every verifier have to be online?

No. The engine computes without a network; keys, status lists and anchors are provided in advance. This allows verifiers even in isolated networks.

### How many verifiers does a flow need?

At least one before every action with consequences. For payments and disputes, a second one after execution that checks the receipt is worthwhile.

### Is a verifier the same as a firewall?

No. A firewall decides on connections based on addresses and rules. A verifier checks evidence of the authority for a specific action and records the result in a recomputable certificate.

## Sources

- [KYA method](https://knowyouragent.ch/en/method)

## Related terms

- [Decision token](https://knowyouragent.ch/en/knowledge/glossary/decision-token)
- [Fail-closed](https://knowyouragent.ch/en/knowledge/glossary/fail-closed)

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Quelle: https://knowyouragent.ch/en/knowledge/glossary/verifier · KYA – Know Your Agent