---
term: "Idempotency key"
category: "Authentication and security"
url: https://agenticopenfinance.com/glossary/idempotency-key
source: AgenticOpenFinance glossary
---

# Idempotency key

> A unique value sent with a request so that a retry is recognised and not carried out twice.

An idempotency key is a unique value a client sends with a request so that, if the request is retried, the server recognises it and does not perform the action twice. The Agentic Commerce Protocol's delegate payment interface accepts one and rejects a reused key with different parameters as a conflict. Agents retry and resume often, and some frameworks re-run steps after an approval pause, so every money-moving call should carry one.

Related terms: [Delegated payment](https://agenticopenfinance.com/glossary/delegated-payment.md), [Audit trail](https://agenticopenfinance.com/glossary/audit-trail.md), [Checkout session](https://agenticopenfinance.com/glossary/checkout-session.md), [Excessive agency](https://agenticopenfinance.com/glossary/excessive-agency.md)