Mono-interpretable would come to mind, which describes a concept of mono-interpretability.
It is the antonym of poly-interpretable.
To react to the comment below (Shouldn't the antonym of poly-interpretable be poly-uninterpretable? Jokes aside I don't see a one vs many relation as being an antonym.)
Mono- is often, if not always, used to form the antonym of a word formed with the poly- prefix.
A usual antonym for polygamy is not poly-nongamy or poly-singleness or anything describing the idea that someone is multiple times not married. The antonym for married to several people is married to one person: monogamy.
Likewise, the antonym for polytheism is not poly-atheism or any other concept describing the not-believing in several deities, but rather a concept describing a believe in one, as opposed to many, deity: monotheism.
One v.s many are perfectly fine antonyms if the one-ness or many-ness are defining properties of the concept. After all, in polygamy, the big point is not that people marry, but that they do it multiple times. Polytheism is not about theism per se, but about the fact there are multiple gods.