2.4free~6 min

Format — shape the output before it arrives

Artifact: one prompt with a three-line format spec — shape, schema, edge case

1. Why format is the cheapest leverage

Of the five parts, format gives you the biggest lift per word.

When you skip format, the model picks. Usually prose. Usually with hedges. Usually with markdown headings you didn't want. Then you re-read it three times trying to find the answer.

When you specify format, you choose the shape of the answer before it arrives. That has three downstream effects:

  1. You can scan it faster.
  2. You can pipe it to a tool (JSON, CSV).
  3. The model has to commit to specifics — severity: high instead of this is a fairly serious one.

The third effect is the underrated one. Format forces precision.

2. Three format moves, ordered by leverage

In rough order of how much they tighten the output:

  • Output shape. Return JSON only. No prose. One sentence per item. A diff, not the full file.
  • Schema. Spell out the fields. { severity: "high"|"med"|"low", line: number, fix: string }. The schema is contract — the model fills in your structure.
  • Negative space. Tell the model what not to include. No commentary. No preamble. Skip the introduction.

The third move catches the rookie mistake — the model adding "Here's the review you asked for:" before the actual review. One line of no preamble removes it.

3. Prose vs. JSON, same task

textVibe — free-form prose
Find any bugs in this function and tell me about them.

The output: a wall of text with headings, some bullets, some hedging. You scan for the bugs and they're somewhere in there.

textSpec — JSON, schema, no preamble
Find bugs in the function below. Return JSON only — no preamble, no commentary.

Schema:
{
bugs: [
  { line: number, severity: "high" | "med" | "low", description: string, suggested_fix: string }
]
}

If there are no bugs, return { "bugs": [] }.

Now the output is a structure you can pipe into anything. The diff between two runs is immediately visible. The model's hedging is gone — it has to commit to high/med/low and a specific line number.

4. The pattern, for any task

A general template, three lines:

  • Return [format]. No preamble.
  • Schema: [if structured].
  • If [edge case], return [explicit value].

Most prompts get noticeably better the moment they include those three lines, regardless of task.

5. Try it