Your deployed legal assistant shows great performance but occasionally repeats incorrect legal terms.

The decisive point is failure isolation: Option D keeps the agent’s decision path observable instead of burying behavior inside one prompt or one service. The stack-level anchor is clear: the Agent Toolkit model is to expose tools as reusable workflow components; that is what makes multi-tool agents testable under schema changes. The selected option specifically D states “Add fact-checking steps using external tools during generation”, which matches the operational requirement rather than a superficial wording match. Factual reliability improves when generation is checked against external authoritative sources. Hardcoded snippets age badly and do not generalize across legal contexts. The implementation detail that matters is schema-bound tool invocation, typed parameters, timeout envelopes, retry policy, and traceable function execution. The distractors fail because embedding tools inside the agent loop makes security review, timeout handling, and version control unnecessarily difficult. That is the difference between an agent that works in a notebook and an agent that remains reliable in production.