dnd 5e – Can you use Dyrrn’s Tentacle Whip to make a melee spell attack

Dyrrn’s Tentacle Whip is a whip, which is a melee weapon.

The Whip appears in the Martial Melee Weapons table of the PHB. Dyrnn’s tentacle whip says:

Weapon (whip), very rare (requires attunement)

So Dyrnn’s Tentacle Whip is a melee weapon. When attacking with a melee weapon, you make a melee weapon attack, not a melee spell attack.

The Tentacle Whip does not extend your reach for melee spell attacks.

The Reach property of weapons says:

This weapon adds 5 feet to your reach when you attack with it

If you are casting a spell that calls for a melee spell attack, you are not attacking with Dyrnn’s Tentacle Whip so the Reach property of the weapon does not apply.

Of course, a DM could rule that it does count, and from a flavor perspective this seems reasonable, but that would make this magic item extremely powerful, far more powerful than it is otherwise.