Share your shortest system prompt that actually changed the output

For code review: Only comment on bugs. Cut review length by 80% and made people actually read them.

Answer, then explain. Stops it from warming up for three paragraphs.

If unsure, say which fact you are unsure about. Not short, but it turned vague hedging into useful flags.

Use the user's words. For a support bot — customers stopped getting answers phrased in our internal jargon.

You are talking to a senior engineer. Does more than you would expect.