Most agent demos work beautifully on stage and fall apart the first week in production. The reason is almost always the same: the demo treats tool-calling as a happy path, and production is nothing but edge cases. A tool times out. A model hallucinates an argument. The agent loops on itself and burns through your token budget. After shipping a few of these systems, I have learned that the durable design question is not "can the agent call a tool" but "what happens when the tool call goes wrong."