---
title: "Error reference: all KYA reason codes explained"
url: https://knowyouragent.ch/en/method/errors
lang: en
updated: 2026-10-12
license: © Innopulse Consulting GmbH
---

# Error reference

Each check in the certificate names a reason code when needed. This reference explains what triggers each code and how to fix it.

The engine reports a status for each of the ten checks: valid, invalid, not checked, not present, unknown or recognized. Where the status needs an explanation, the certificate names a reason code. The codes are stable and the same in all versions of the engine; new codes are added only with a new version.

Not every code is an error. Some describe missing evidence that makes a result indeterminate, such as a missing status list. The following pages explain the codes per check.

## Codes by check

- [Format and schema](https://knowyouragent.ch/en/method/errors/format)6 codes: format_unknown, format_recognized_not_supported, not_evidence_key_material, malformed, required_claim_missing, format_not_supported

- [Cryptographic integrity](https://knowyouragent.ch/en/method/errors/cryptographic-integrity)13 codes: signature_invalid, no_key, unsupported_alg, disclosure_digest_mismatch, disclosure_unreferenced, disclosure_duplicate, kb_jwt_invalid, chain_hash_mismatch, chain_link_broken, binding_mismatch, manifest_mismatch, no_crypto_material, tsa_signature_invalid

- [Issuer](https://knowyouragent.ch/en/method/errors/issuer)3 codes: issuer_key_not_trusted, kid_issuer_mismatch, no_signed_artifact

- [Agent and principal](https://knowyouragent.ch/en/method/errors/agent-and-principal)5 codes: agent_mismatch, principal_missing, agent_missing, no_credential, credential_is_not_a_mandate

- [Mandate validity](https://knowyouragent.ch/en/method/errors/mandate-validity)3 codes: expired, not_yet_valid, mandate_not_included

- [Scope of the action](https://knowyouragent.ch/en/method/errors/scope-of-the-action)7 codes: action_not_in_scope, amount_exceeds_limit, currency_mismatch, counterparty_not_allowed, mandate_without_scope, constraint_not_supported, no_action

- [Delegation chain](https://knowyouragent.ch/en/method/errors/delegation)4 codes: no_delegation, delegation_broken, delegation_scope_widened, delegation_key_missing

- [Revocation](https://knowyouragent.ch/en/method/errors/revocation)7 codes: revoked, suspended, status_value_unknown, status_list_not_provided, status_list_unverified, status_list_invalid, no_status_reference

- [Execution receipt](https://knowyouragent.ch/en/method/errors/execution-receipt)4 codes: receipt_decision_mismatch, receipt_mandate_mismatch, no_receipt, no_decision_reference

- [Timestamp](https://knowyouragent.ch/en/method/errors/timestamp)6 codes: tsa_malformed, tsa_imprint_mismatch, tsa_anchor_not_provided, tsa_not_trusted, tsa_target_unknown, no_timestamp

## Dependencies between checks

### `prerequisite_failed`

**Not checked because an earlier check failed.**

**Cause:** The check was not run because an earlier check it builds on failed. Without a readable format, for example, no signature can be verified.

**Fix:** First fix the code of the earlier check. The engine then runs the dependent checks again.

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Quelle: https://knowyouragent.ch/en/method/errors · KYA – Know Your Agent