I really wish there was better pencil support in apps on the iPad. I'm working remotely from the rest of the team which means I can't sit with someone and draw

I really wish there was better pencil support in apps on the iPad. I'm working remotely from the rest of the team which means I can't sit with someone and draw out a diagram when I'm trying to explain things. If you're communicating with Slack there's pretty much no support at all for it. Is there any chat app that has first party support for pen? I don't want to crawl the web for some sketch webapp and go through hoops just to sketch a couple of boxes and send them.