Built an MCP tool called Ownhand. It learns your writing style, so your Agent can hook into it automatically when writing a message or an email. It tracks style templates for any domain (chat, formal email, etc.) and adds rules over time to better match your voice.
This idea was born during the Opus 5 era (please, never again), but it's still useful today (I use it dozens of times a day as a freelance consultant).
It's entirely AI native, so you don't have to do anything, your agent handles it. It grows with you as you use it, and you can even create custom domains, i.e. reddit comments, texts to family members (jk).
You teach it by simply sending it the edited version (what you sent irl) and it learns implicitly from that. Your agent makes calls to the MCP with the domain, recent message history, extra context, and even who it's being sent to. Ownhand handles all of it.
I'm wondering how you guys handle this issue; I'd love to hear your approaches. I've tried skills before, but it's just really bad at it, even with Opus 5.5.