Can you use the Jinx Rocket effect when conquering without cards in hand?

Ruling: No, you need a card in hand to discard in order to bring Rocket back. The discard is a cost to return Rocket.

Nuances:

• This concept does not apply to cards like Chemtech Enforcer, which don't use the 'to [do stuff]' templating
• For effects without the cost templating, you can activate the effect but if you don't have a card in hand by the time you resolve it, you won't get the unit back