Quick answer: The PromptEval Prompt Quality Report scored over 1,000 real prompts across 12 use cases. The average was 52 out of 100, and only 8% reached "good" (75+). The strongest single predictor of a good prompt is whether it defines its output format, worth 27 points on average. In 9 of 10 prompts, the weakest dimension was robustness.
This is the PromptEval Prompt Quality Report. Over 1,000 real prompts have been scored on and .
Short prompts almost never win
Length is not a virtue on its own, but the data is blunt about the floor.
| Prompt length | Avg score |
|---|---|
| Under 200 characters | 27 |
| 200 to 800 | 45 |
| 800 to 2,000 | 59 |
| Over 2,000 | 67 |
The score climbs steadily with length, not because padding helps, but because you cannot fit a format spec, a couple of constraints, and an example into one sentence. A one-line prompt scored 27 on average, squarely in the failing tier.
Some fields write better prompts than others
Broken down by use case, the pattern is telling. Fields where a wrong answer carries a real cost wrote the most careful prompts.
| Use case | Avg score |
|---|---|
| Healthcare, HR, research | 56 to 60 |
| Data analysis, content, support | 53 to 55 |
| Coding, education | 51 to 52 |
| Marketing, creative | 47 |
Marketing and creative prompts scored lowest, usually because they lean on vague quality words like "engaging" or "compelling" instead of a concrete spec. The model cannot optimize against a vibe.
Before and after, with the score
Here is a weak prompt and the same request rebuilt with the levers above. The jump shows where the points came from.
Before (score 34): "Write a support reply for this customer message." No role, no format, no constraints, and no handling for a message that is not actually a support request.
After (score 78): "You are a customer support agent for a SaaS product. Given a message, reply in 2 to 3 sentences, friendly and specific, and never promise a refund or a timeline. If the message is not a support request, reply only with: 'Could you tell me what you need help with?'"
Same task. The role, the format ("2 to 3 sentences"), the constraint ("never promise a refund"), and the edge-case rule together moved it 44 points, from failing to good.
What the data means for your prompts
Taken at face value, most weak prompts move up a tier with four additions:
Format: state the exact shape of the answer (length, structure, fields). Worth the most.
Constraints: one or two "do not" rules that fence off the ways it can go wrong.
Role: one line telling the model who it is and what it is for.
Edge case: what to do when the input is bad or missing. The line nobody writes.
You do not have to guess whether your prompt has these. Paste it into the free , and this one explains the four dimensions.
SOCIAL SHARE CARD GENERATOR