How do you know if a reaction is endothermic?

If the products are at a higher energy level than the reactants, the reaction must have absorbed energy. If you have to heat the reactants to keep the reaction going or if it cools down during the process, the reaction is endothermic.

If you have to heat the reactants to keep the reaction going or if it cools down during the process, the reaction is endothermic

i think its the first one