I believe there's a legal phrase (in Latin) that basically means that the expert in a relationship bears more responsibility than the non-expert. Sample, if someone is building a house, the builder is more responsible in making things clear and understood because they are the expert in this relationship (they do this for a living on a daily basis). Do you know what this phrase is?
the legal phrase that you are looking for could be “Caveat venditor” meaning:”Let the seller beware” just to point out the principle that a person who sells something is responsible for making sure that it is in good condition and works properly.
In short, “Caveat venditor” is a "warning to the sellers that, unless they expressly disclaim any responsibility, they will be held liable if the sold items are found defective in any way or vary from the specifications".
Such a legal phrase calls to mind another Latin maxim which reads “Nemo potest alicui laedere” meaning “Nobody can harm anybody else” just to emphasize the principle of responsibility.
Similarly we could say for example “Caveat structor” to mean “Let the builder beware” with reference to the builder who must be responsible in making things clear and understood, as you say.
To conclude, I hope that “Caveat venditor” and “Nemo potest alicui laedere” are what you are looking for.
In Latin there is another phrase, i.e. "Caveat emptor", meaning "Let the buyer beware", which states that the purchaser is responsible for checking whether the goods suit his need, as
a person who buys something is responsible for making sure that it is in good condition, works properly, etc.