Thanks for the update! Have you tried the Virtual HTTP Switch device handler linked above?
The Virtual HTTP Switch enables you to create a device in SmartThings which can call HTTP endpoints on your network which sounds like it would work perfectly for your use-case. You can then authorize these to SharpTools and use them like normal Thing tiles.
Other thoughts (tap to expand)
Based on the comment about a window opening, I assume you are currently using a Hyperlink tile within SharpTools. If the Node.js server had a valid SSL certificate (eg. IF it was HTTPS, you could use the Hyperlink REST API syntax - which it likely isn’t if it’s a local Node.js setup)