There is no such thing as a safe or "official" free unlock tool. The risk of losing your entire Activision account and compromising your personal data far outweighs the reward of a digital weapon skin.
: Activision's Ricochet anti-cheat system is designed to detect third-party software that manipulates game data. Inventory Verification free mw 2019 unlock tool link
While the legality can vary by jurisdiction, using such tools often exists in a legal gray area. Users can face penalties, though enforcement can be inconsistent. There is no such thing as a safe