{
 "id": "idempotency-key",
 "name": "Idempotency-Key header",
 "aliases": [
  "Idempotency-Key",
  "idempotent tool call"
 ],
 "definition_md": "An **`Idempotency-Key`** is a unique client-generated token attached to an HTTP `POST`/`PATCH` request or agent payment invocation so that if an agent retries after a network timeout, the server recognizes the duplicate and returns the original result rather than executing the action or charging the user twice. It is standard across **Agentic Commerce Protocol**, **x402** / **MPP** payment retries, and non-idempotent MCP tool annotations (`idempotentHint: false`). Used by: agentic-commerce-protocol, mpp.",
 "step": "act",
 "related_protocols": [
  "agentic-commerce-protocol",
  "mpp"
 ],
 "sources": [
  {
   "url": "https://github.com/agentic-commerce-protocol/agentic-commerce-protocol",
   "date": "2026-04-17",
   "label": "VERIFIED"
  }
 ],
 "part_of": null,
 "group": null,
 "url": "https://agenticweb.wiki/terms/idempotency-key/",
 "okf_url": "https://agenticweb.wiki/okf/terms/idempotency-key.md",
 "category": "act",
 "type": "term"
}