Have you tried recording commands:
You can step through the commands one-by-one up to the point where you want to make changes:
Then record making the tangent arc.
I suggest you set the selection type to index:
I guess the above is good general advice, but in this example, you can’t see anything until the body is created:
You could call this when only one tooth is made, but it’s going to need a closed boundary of curves.
If you want to see the curves before the body is created, you could remove some lines in the loop, and do the following after the loop to see the curves it made:
for crv in boundary: