What do you mean? You can force JSON with structured output.

It was just an example though, in real-world scenarios, sometimes I have to tell the AI to respond in a specific strict format, which is not JSON (e.g. asking it to end with "Good bye!"). Claude is the one who is the worst at following those type of instructions, and because of this it fails to return to correct answer in the correct format, even though the answer itself is good.