# Rubric: L-USABILITY

**Lens:** `L-USABILITY` · **Density:** D-LOW (Top N) · **Axes:** OPS, RDB, CMP

## Criteria

1. Time-to-first-success for the primary persona (CLI user, API client, end user).  
2. Help/error messages actionable?  
3. Defaults safe and obvious?  
4. Breaking changes discoverable?  
5. Consistency of UX vocabulary.

## Citations

| Work | Point |
|------|-------|
| ISO 9241-11 | Usability definition (effectiveness, efficiency, satisfaction) |
| Nielsen — 10 Usability Heuristics | Error prevention, recognition vs recall, consistency |
| Command-line interface guidelines (clig.dev) | When target is a CLI |

## Pros / cons

| Pros | Cons |
|------|------|
| Often the actual open-source adoption gate | Easy to confuse with product taste — keep heuristics cited |
| Ties CMP (docs claim vs reality) | Libraries without UX still need API ergonomics — reframe axis to RDB/MNT |

## Top-N bias

Prefer findings that block strangers over aesthetic CLI color debates.