Stretchable parentheses in text labels in Graphics

In graphics, Text objects render in TraditionalForm. In TraditionalForm, parentheses are used instead of square brackets. So you can achieve what you want by using an expression with an invisible head:

Graphics[Text[Style[Invisible[""][1/2,Sqrt[3]/2],Black,12],{-1.1,.8}]]

There are other ways to achieve this behavior, but they require learning a bit about how boxes work.

<< MaTeX`

Plot[0, {x, -1, 1}, 
    Epilog -> { Point[{-1/2, Sqrt[3]/2}], 
            Inset[MaTeX[
                    "\\left(-\\frac{1}{2},\\frac{\\sqrt{3}}{2}\\right)"], {-1/2 + 
                        0.1, Sqrt[3]/2 - 0.3}]}]