OpenAI shipped guardrails in the Agents SDK last month. Input guardrails. Output guardrails. Tool call guardrails. The API is clean. The docs are good. A lot of builders are excited. I want to be clear: these are real. They solve real problems. They just don't solve the one that costs you money. What OpenAI's guardrails actually do OpenAI's guardrails are validators. They inspect what goes into and out of your agents at runtime. Input guardrail: run logic before the agent processes a message. Block it, redirect it, log it. Output guardrail: run logic after the agent produces a response. Flag it, filter it, hold it. Tool call guardrail: intercept a tool invocation before it fires. Approve or reject based on your rules. These are behavior controls. They answer the question "did my agent do the right thing?" That question matters. But it is not the question that generates a $47,000 AWS invoice. The gap OpenAI's guardrails have no concept of spend. There is no budget_usd parameter. No on_exceed hook.…