architecture
Idempotency
An operation is idempotent if it can be applied multiple times without changing the result beyond the initial application.
Agentic systems must be resilient to retries. If an agent tries to call a "charge payment" tool, the network times out, and the agent retries, it must *not* charge the user twice. Building idempotent tools—often by including a client-generated unique `idempotency-key`—is a mandatory best practice for any MCP server dealing with side-effecting operations.