Most generally, transactions can be freely negotiated by either party. I.e. no force or fraud. Contracts need to be enforceable. Individual liberties must be guaranteed.
> working well
Delivering on prosperity.
To clarify, imperfect information is not fraud.
Force in this context is something proactively applied, such as your signature will be on the contract or your brains. Force is not withholding something you have that the other party needs.
Charity, voluntarily helping others in need, etc., is perfectly in line with free market principles. Unions are perfectly in line, too, although laws bestowing monopoly powers on unions are not.
A free market does not have to be a perfect free market in order to deliver prosperity. Even small amounts of free markets can have outsized positive benefits, as the Soviet Union discovered when it allowed farmers to farm small plots, sell the produce, and pocket the proceeds.
Life expectancy was a good proxy in the 1800s because it improved dramatically, but now it has asymptotically approached a biological limit so is less useful. The same for average height.
These requirements are not remotely necessary for free markets to work and work well.