The uncertainty is indicated though by the error in the position of each control point. If you have a decent selection of control points, then you have a sampling of the calibration error.

Agreed that its purpose is not to make a map. It is designed to handle the case where the camera is in the same position for every picture.

That's the thing about the non-mrcal tools: they don't give you good feedback. The pixel errors do NOT indicate uncertainties. You can trivially prove this to yourself: throw away lots of your data and re-solve. The pixel errors then decrease. But we can all agree that throwing away data gives you worse solves, right?

mrcal actually gives you real uncertainties, so you can get proper feedback about what you're doing. There's a whole lot to say on this topic. If you're interested, read the docs. The "tour of mrcal" page gives a good overview.