Question 1
An operations team runs a high-traffic legal-research assistant on the OpenAI Agents SDK. The main agent is a large, expensive model that performs multi-step retrieval and reasoning. The team adds a small, fast model as an **input guardrail** whose only job is to decide whether an incoming request is within the assistant's remit. Which TWO statements correctly describe why placing this cheap check as a guardrail — rather than folding the same judgement into the main agent's instructions — is sound design?
A. It stops out-of-scope requests before the expensive agent starts its multi-step work, avoiding the cost and latency of a full run that would have been rejected anywayCorrect answer
Correct. Cost and latency savings are an explicit motivation for input guardrails in the Agents SDK: a cheap, fast model screens the request so the expensive agent is never invoked on work that will be thrown away.
B. The scope decision is enforced deterministically outside the agent's reasoning, so it cannot be talked around by a crafted user message that reshapes how the agent reads its own instructionsCorrect answer
Correct. Instructions are input to the model's reasoning and can be undermined by prompt injection or simple drift; a guardrail is a separate check on the run whose tripwire does not depend on the main agent choosing to comply.
C. Registering the guardrail improves the main agent's reasoning quality, because the agent learns from the guardrail's rejections over successive runs
Assumes guardrails train or improve the agent. Guardrails are runtime checks around a run; they do not update model weights or accumulate learning, and the main agent's reasoning ability is unchanged by their presence.
D. The guardrail becomes an additional tool in the agent's toolset, which the agent invokes when it is unsure whether a request is in scope
Conflates a guardrail with a tool. A tool is called at the agent's discretion during reasoning; a guardrail runs as part of the run's machinery whether or not the agent wants it, which is precisely what makes it a reliable control.
E. Guardrails are documentation-level policy statements that record intent for auditors but leave the run's behaviour unchanged
Treats guardrails as optional decoration with no runtime effect. A guardrail whose tripwire fires actually halts the run, so it changes behaviour rather than merely declaring intent.
Explanation
Two properties justify guardrails as a separate concern from the agent's instructions. First, economics: a cheap, fast guardrail model can reject an off-remit request before the expensive main agent begins a multi-step run, saving the cost and latency of work that would be discarded. Second, enforcement: instructions are consumed by the model's own reasoning and can be drifted away from or subverted by a crafted input, whereas a guardrail is evaluated outside that reasoning and its tripwire halts the run regardless of what the agent concludes. Guardrails do not train or otherwise improve the agent — they are runtime checks, not a learning signal — and they are neither tools the agent may elect to call nor inert policy documentation, since a tripped guardrail actively stops execution.