An agent-native product isn't a chatbot bolted onto a CRUD app — it's an MCP server that lets an agent do things. Read invoices, create expenses, mark a client overdue. The demo is easy. The part that decides whether the thing survives contact with real traffic is the layer nobody screenshots: what happens when a write is sent twice.
This is the unglamorous half of agent-native engineering. Every write operation an agent can invoke needs idempotency, safe retries, and typed recoverable errors — not as a nice-to-have, but as the difference between a product and a liability. Here's why, and how to build it.
Agents turn "at-least-once" from a footnote into a daily event
Distributed systems people have known forever that networks give you at-least-once delivery, not exactly-once. A request goes out, the response gets lost on the way back, the caller doesn't know if the write landed, so it retries. With a human clicking a button, this is rare enough to hand-wave.
Agents remove the hand-wave. Three things about how agents call tools push duplicate writes from "edge case" to "Tuesday":
