Tone Is a Choice, Not an Accident
Tone problems are rarely intentional. Nobody sets out to sound dismissive. It happens because tone is the one part of writing most people never consciously edit.
Tone lives in the small words
"As I mentioned", "just", "obviously", "per my last message" — none of these change the facts, and all of them change how the message feels.
Because they are small, they survive editing. Scan for them specifically.
Written text loses the softening
Spoken, "can you resend that" carries a shrug. Written, it can read as an accusation. Text strips the tone of voice and leaves the reader to supply one, usually the least charitable available.
Add back what the medium removed — a reason, a thank-you, a single word of context.
Pick the tone before writing
Decide in one word what the message should feel like — direct, warm, apologetic, neutral — then write toward it. Tone chosen up front is consistent; tone discovered mid-draft wobbles.
It also makes editing objective: you are checking against a target rather than a mood.