My AC not cold as it should be. Add some refrigerant. Use 134a off the shelf? on 2002 Toyota Prius

I just want to add some refrigerant. This is the first time in 11 years its not as cold as it should be. Can I just follow normal 134a instructions? This is not the electric compressor, it runs from a belt on the engine.

Asked by for the 2002 Toyota Prius
its best to use a set of a/c manifold guages to recharge the system.its safe and accurate.those other recharge kits are just a hack way of refilling the system.its potentionally unsafe n can ruin your a/c system.