Some post-separation texts are not really about the thing being texted. A pickup time becomes a referendum on respect. A bill becomes a fight about the whole marriage.
The basic formula
A calmer text usually has three parts: the topic, the needed answer, and the deadline if there is one.
Template: Hi. I need to confirm [specific thing]. Please let me know by [day/time]. Thanks.
When you need a boundary
A boundary text is not a speech. It is a short line about what you will or will not continue doing.
Template: I am not available to discuss this by text. Please send logistics only.
Clear. Boring. Specific. The text does not need to win the divorce. It only needs to move the next step forward.