Mine isn’t a custom tool. Rather it is a custom options-setting command that should work with any tool (see this post for the code). For example, while sketching, measuring, drawing a circle, etc.
Since view.refresh does not invalidate the content of the VCB, my hack activates “no tool”, then reactivates the formerly active tool, which presumably causes that tool to repopulate the VCB with fresh content, and also update the tooltip. I don’t know internally whether it’s suspend/resume-ing or activate/deactivate-ing. But the fact that it works with a built-in tool selected through the UI indicates to me that they are now (SU2018) utilizing the tool stack for user selection as well as direct tool_push. I haven’t tested it with every tool, but it works with everything I’ve tried, including sketch tool, circle, rectangle, tape-measure, etc.