Storing a tool state in a tag is possible, but a bit unusual. But generally you are on the right track. Tags are also internally often used as hidden data containers. When you write a modelling tool, you probably already found out that points and polygons are are actually stored in hidden tags on objects.

I am not sure though if using tags in tools is a good advice, as injecting all that data all the time into the scene graph is probably not the fastest. It depends a bit on what you are doing, but in general the solution is a bit unusual.

Cheers,
Ferdinand

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About your First Question

You could look at our edgecuttool.cpp C++ SDK example, it demonstrates both the usage of undos and cinema::InteractiveModeling_Restart, i.e., rolling updates. In some cases InteractiveModeling_Restart will not cut it you have to un-roll your undos yourself or even not use undos at all for rolling updates and instead work with a tool finalization logic.

By chance I just wrote an example for the latter for the upcoming Python SDK. You will not be able to run it, as the customer release version is missing the Python API to deal with SDS weights, but you can have a look at its code. The idea is simple: Establish a ground truth and operate based on that. But for modelling tools and especially tools that add or remove geometry using undos and InteractiveModeling_Restart should be preferred when possible, as it will be usually faster, as the cinema core can pull some tricks you cannot as a third party.

Cheers,
Ferdinand

Please understand that this example is a preview and might be subject to change.
py-cmd_tool_finalization_2026_2.zip