True consent also requires being fully informed - having all pertinent data that all parties know of. (Obviously, if there is something unknown by any of the parties but it is pertinent, it cannot be expected to be impactful on whether consent is valid.)
A voluntary action (voluntainess) is one made with no pressure from any other party. Conditions necessary for agreement are that all parties are fully informed and accept the proposal in full. Consent can be withdrawn when it is discovered that some aspect was deliberately hidden (not being fully informed). When the agreement was based on incomplete data.
