Chapter 1 · Practice 3 of 4
Say what to do, not only what to avoid
Why it matters
Negative instructions name the thing you do not want, which keeps it in view. Positive instructions describe the target directly.
Anthropic's guide gives this as its first tip for controlling format: tell the model what to do instead of what not to do.
| Instead of | Write |
|---|---|
| Do not use Markdown | Write in plain prose paragraphs |
| Don't be too long | Answer in two or three sentences |
| Don't make things up | Answer only from the documents below; if they do not contain the answer, say so |
Keep a short list of hard limits where you need them, but make sure each one sits next to a positive description of what good output looks like.