As I am mainly a Java guy it has burnt into me to never rely on .toString() output for code flow. It seems to me that this is somewhat similar (or has the Unix world a gentlemans agreement that output has an API contract). I'd never touch anything where I couldn't enforce (preferably typed) output to rely on especially in a security context. I think I have already seen command line tools which can return structured content (json, xml) with a switch (I don't remember which, though).

> I have already seen command line tools which can return structured content (json, xml) with a switch

That happens. It doesn't need to a standard format like that however. Some command like tools add a porcelain option that produces output for scripting (ie no ansi color codes, easy to parse, etc). That works well too.

awscli tools can generally do so.

This is literally how all Linux and Unix CLI tools interoperate. Would be great to see wider adoption of something like PowerShell's ouput model.