Can I use it as a system prompt?

[mirumirumi]

This “Thinking Claude” effect is great, but the downside is that it uses more tokens.
If I put this in the system prompt instead of the user prompt, would it have the same effect?

Also, I would like to know what would happen if we use it in the API.

[lumpinif]

I think you could use it in the API and put it in the system prompt.