The requirements ask for behavior that applies to every future conversation, improves routing for representative compound inputs, and standardizes final output with minimal application-code change. Few-shot instruction examples satisfy all three by demonstrating both the desired routing decision and the expected schema-compliant response for representative cases. Repository-wide constraints list rules but do not demonstrate how ambiguous compound requests should be handled. Per-request prompt cues are not durable across future conversations and would require application logic to inject them repeatedly. System role instructions define domains and objectives but provide less behavioral specificity than examples. Microsoft AI-500 prompt-engineering objectives explicitly include examples and dynamic prompt techniques for shaping complex agent behavior. Therefore C is the strongest design. The implementation should also preserve clear inputs and outputs around this step so that later agents receive only the information they require. This improves debuggability and keeps token, permission, and state growth under control as the workflow becomes more complex.

Official Microsoft reference: AI-500 Study Guide - advanced prompt engineering