How do you feel about Cis authors writing trans characters?

I'm an author starting my next novel, and I would like to write one of the secondary characters as being trans (mid-20s, either MTF or non-binary). Generally, I want to know the thoughts/opinions from trans/nb individuals --- How do you feel about Cis writers writing trans characters?

What are the big no-nos or telltale signs of bad writing of trans characters?

If a writer, as I am, includes a trans character simply to provide representation, even if the trait isn't strictly necessary for the main plot, does that bother you? Does it depend? Or do you wish that it would happen more often?

What might you want a writer as myself to know or keep in mind before going into this?

Finally, if there are any recommendations of trans literature for me to read beforehand, I would very much appreciate it. Thank you.