Why shouldn't data be modified on an HTTP GET request?

Question

I know that using non-GET methods (POST, PUT, DELETE) to modify server data is The Right Way to do things. I can find multiple resources claiming that GET requests should no

Answer 1

I'm kind of looking for more than just "it doesn't make sense semantically" or "it makes things ambiguous."

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I don't care what The Right Way to do things is, it's easier for us

Tell them to think of the worst API they've ever used. Can they not imagine how that was caused by a quick hack that got extended?

It will be easier (and cheaper) in 2 months if you start with something that makes sense semantically. We call it the "Right Way" because it makes things easier, not because we want to torture you.