[Smaug123]

Longhand matrix notation itself is quite good at this. It all but guarantees that you've specified the right number of components in the matrix, and it plays to human strengths in making it easy to check that a matrix is e.g. diagonal or upper-triangular.

I'm going to claim that string diagrams have reasonably good error-detection properties, too, again because they lay facts out in space in a way that humans are quite well optimised for.