At production scale, Option B preserves separability between reasoning, state, tools, and runtime operations. A microservice tool layer lets a calculator, search adapter, and business API evolve independently while the agent sees uniform contracts. That is the maintainable path when the tool catalog grows beyond one workflow. Operationally, the design depends on a tool boundary where every API has declared inputs, declared outputs, validation, retry behavior, and instrumentation. The selected option specifically B states “Microservice-based tool architecture with standardized interfaces”, which matches the operational requirement rather than a superficial wording match. The alternatives would look simpler in a prototype, but relying on the model to infer API behavior invites fabricated endpoints, malformed arguments, and brittle production behavior. For a production build, NVIDIA’s agent tooling favors explicit function specifications and observable execution paths instead of free-form API narration in the prompt. It also creates clean evidence for audits, incident review, and root-cause analysis when behavior drifts.