nw-fp-usable-design

# FP Usable Design Make functional code usable. The developer is the user of your design. Apply usability thinking to code organization, naming, and architecture. Cross-references: [fp-domain-modeling](../nw-fp-domain-modeling/SKILL.md) | [fp-hexagonal-architecture](../nw-fp-hexagonal-architecture/SKILL.md) | [fp-algebra-driven-design](../nw-fp-algebra-driven-design/SKILL.md) --- ## 1. Core Insight [STARTER] The user of software design is the developer, not the end user. When developers struggle, blame the design, not the people. Pressure, team churn, unclear specs, and noisy environments produce unusable designs. Improve the design. --- ## 2. Five Evaluation Goals [STARTER] | Goal | What It Means | How to Assess | |---|---|---| | **Learnability** | How quickly a new developer becomes productive | Timed tasks for unfamiliar developers | | **Efficiency** | How fast common tasks are performed | Count unnecessary navigation and decisions | | **Memorability** | How easily proficiency returns after time away | What do returning developers re-learn? | | **Error resistance** | How many bugs the design induces | Track bug locations; ask "what design change prevents this category?" | | **Satisfaction** | How pleasant to work in the codebase | Developer interviews, retrospectives | --- ## 3. Naming Conventions [STARTER] ### Domain Language in Function Names Use domain expert's vocabulary, not mathematical conventions or technical jargon. No `OrderFactory`, `OrderManager`...