# Idempotency

Source: https://customlabs.io/glossary/idempotency/
Updated: 2026-09-13

Agents

# Idempotency

An idempotent operation produces the same result no matter how many times it runs.

Calling it twice does nothing that a single call had not already done.

For a tool that writes, sends, or deletes, idempotency is what makes a retry safe.

It is usually enforced with a unique key passed on every retry of the same call.

Without it, a timeout followed by an automatic retry can execute the same mutation twice.

[The Agent Tool Interface](https://customlabs.io/tool-design/)[Failure mode: Retry-amplified spend](https://customlabs.io/failure-modes/retry-amplified-spend/)

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## Related terms

[Tool Contract A tool contract is the schema a tool exposes to a model.](https://customlabs.io/glossary/tool-contract/)[Tool Calling Tool calling lets a model request a structured action instead of only generating text.](https://customlabs.io/glossary/tool-calling/)

## More in Agents

[Agent (Agentic AI) An agent is an LLM given a loop, memory, and tools it can call.](https://customlabs.io/glossary/agent/)[Model Context Protocol (MCP) MCP is an open standard for connecting LLM applications to tools and data sources.](https://customlabs.io/glossary/model-context-protocol/)[Context Engineering Context engineering decides what occupies a model's context window at every step, and in what order.](https://customlabs.io/glossary/context-engineering/)[Structured Output Structured output constrains a model's response to a defined schema instead of free-form prose.](https://customlabs.io/glossary/structured-output/)