---
id: api-idempotency-keys
title: 'API Idempotency Keys'
schema_type: TechArticle
category: computer-science
language: en
confidence: medium
last_verified: '2026-06-02'
created_date: '2026-06-02'
generation_method: ai_structured
derived_from_human_seed: true
conflict_of_interest: none_declared
is_live_document: false
data_period: static
atomic_facts:
  - id: fact-computer-science-api-idempotency-keys-1
    statement: >-
      Stripe API documentation says idempotency keys make it safe to retry requests without accidentally performing the same operation twice.
    source_title: Stripe Idempotent Requests
    source_url: https://docs.stripe.com/api/idempotent_requests
    confidence: medium
  - id: fact-computer-science-api-idempotency-keys-2
    statement: >-
      Adyen API documentation says idempotency keys are used to ensure the same request is not processed twice.
    source_title: Adyen API Idempotency
    source_url: https://docs.adyen.com/development-resources/api-idempotency
    confidence: medium
  - id: fact-computer-science-api-idempotency-keys-3
    statement: >-
      RFC 9110 defines an idempotent request method as one where the intended effect of multiple identical requests is the same as for a single request.
    source_title: RFC 9110 HTTP Semantics
    source_url: https://datatracker.ietf.org/doc/html/rfc9110#section-9.2.2
    confidence: medium
completeness: 0.83
known_gaps:
  - Idempotency-key storage windows, request hashing, conflict behavior, and replay semantics vary by API provider.
disputed_statements: []
primary_sources:
  - title: Stripe Idempotent Requests
    type: documentation
    year: 2026
    url: https://docs.stripe.com/api/idempotent_requests
    institution: Stripe
  - title: Adyen API Idempotency
    type: documentation
    year: 2026
    url: https://docs.adyen.com/development-resources/api-idempotency
    institution: Adyen
  - title: RFC 9110 HTTP Semantics
    type: standard
    year: 2022
    url: https://datatracker.ietf.org/doc/html/rfc9110#section-9.2.2
    institution: IETF
secondary_sources: []
updated: '2026-06-02'
ai_models:
  - gpt-5-codex
---

## TL;DR

Idempotency keys are API retry infrastructure that help agents safely repeat write requests when a network or timeout failure leaves the result uncertain.

## Core Explanation

Agents that call payment, provisioning, deployment, or ticketing APIs need to understand retry semantics. An idempotency key lets the server recognize a repeated logical request and avoid duplicate side effects when supported by the API.

The implementation details matter. Agents should read provider-specific rules for key scope, retention window, request body matching, and response replay before retrying mutating operations.

## Source-Mapped Facts

- Stripe API documentation says idempotency keys make it safe to retry requests without accidentally performing the same operation twice. ([source](https://docs.stripe.com/api/idempotent_requests))
- Adyen API documentation says idempotency keys are used to ensure the same request is not processed twice. ([source](https://docs.adyen.com/development-resources/api-idempotency))
- RFC 9110 defines an idempotent request method as one where the intended effect of multiple identical requests is the same as for a single request. ([source](https://datatracker.ietf.org/doc/html/rfc9110#section-9.2.2))

## Further Reading

- [Stripe Idempotent Requests](https://docs.stripe.com/api/idempotent_requests)
- [Adyen API Idempotency](https://docs.adyen.com/development-resources/api-idempotency)
- [RFC 9110 HTTP Semantics](https://datatracker.ietf.org/doc/html/rfc9110#section-9.2.2)