Whose number is this

A phone number is a strong selector: expensive to acquire, hard to change, and used as an account-recovery anchor almost everywhere. It is also the selector investigators get most wrong, because the metadata everyone quotes — the carrier — is frequently stale, and because a large share of numbers now belong to software rather than to a SIM in someone's pocket. Do not call or text the subject; that is contact, not research.

Step 1 — Authorized scope

Read ../../ETHICS.md. Write down subject, objective, in-bounds selectors, out-of-bounds actions, and the governing jurisdiction — which matters more here than in most skills, because reverse phone lookup is specifically regulated in many places. Decide now whether messaging-app contact-discovery checks are authorized; they are interactive.

Done when scope is written and the contact-discovery decision is recorded.