Add simple pointed annotations to equations in Latex, as a CTAN package? Improve writing process

Question

I want to improve the clarity of my Latex articles for readers by adding hyper clear annotations on my equations, like in the two images shown below.

I can imagine a possible solution using Tikz using \draw for lines and \node for text, and this question using tikzmarks has been pointed by @Schrödinger's cat.

Helping the writer's process is the important objective of this question, rather than perfect recreation. For example, using a command like \mathannotation{e=mc^2}{annotation to explain} (fuller example below) within a \begin{equation}{\label{xyz}... block, would be a simple mental transition, and less distracting than thinking about lines and boxes.

Such a solution would encourage ease of use/reuse and improves the writer's process. This could possibly become a future CTAN package for future communicators of science and mathematics.

\documentclass{article}
\begin{document}
\begin{equation}
 \label{xyz}
 \mathannotation{e=mc^2}{some insightful explanation, e is energy, m is mass or matter and c is the speed of light}
\end{equation}

At a basic level equation \ref{xyz} shows us that under the right conditions, energy can become mass, and vice versa.

\end{document}

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Similar questions, that do not address this:

• add remarks to the right,
• text in parentheses below equation,
• text under aligned components, using \underbrace and array - although this is clearest so far.
• custom underlines under text components - could avoid absolute position used by Tikz