How are people preventing duplicate tool execution in AI agents?

I’ve been experimenting with LLM agents calling tools and ran into a reliability issue.

If the agent retries a tool call after a timeout or failure, the side effect can run more than once.

Example:

agent → tool call
timeout → retry
agent retries tool

If the tool triggers something irreversible you can get:

- duplicate payment
- duplicate email
- duplicate ticket
- duplicate trade

Right now it seems like most implementations solve this with idempotency keys or database constraints.

Curious how others are handling this in production agent systems.

Are people solving this in the tool layer, in the agent framework, or in the database?