nw-fp-usable-design

nw-fp-usable-design is a skill for Claude Code from nWave-ai/nWave. It costs 20 tokens per session (2,003 once invoked), scanned A, original, MIT.

A guide to making functional code easier for other developers to use. It covers naming, API design, code organisation, and ways to assess learnability, efficiency, error resistance, and satisfaction.

In plain words
What is it for?
Use it when designing APIs, choosing names, organising functional code, or reviewing how quickly developers can learn and use a codebase.
Why use it?
Functional code can be correct but difficult to understand or use. These patterns help identify design choices that create unnecessary confusion or mistakes.

Skill for Claude Code

Written for Claude Code: disable-model-invocation in frontmatter. Also seen: agent in frontmatter.

Good fit Use it when designing APIs, choosing names, organising functional code, or reviewing how quickly developers can learn and use a codebase.

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Install with agentmods
npx agentmods add skills/nwave-ai/nwave/nw-fp-usable-design
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add nWave-ai/nWave --skill nw-fp-usable-design
Clone the repo
git clone --depth 1 https://github.com/nWave-ai/nWave

Made for: Claude Code.

Wrote this? Show the measurements

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README.md
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Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,003 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00020 $0.02003
Opus 5 $0.00010 $0.01001
Sonnet 5 $0.00004 $0.00401
Haiku 4.5 $0.00002 $0.00200

Measured 5d ago against content hash 4b3aba348ff8, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

nw-fp-usable-design scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

nWave/skills/nw-fp-usable-design/SKILL.md · 238 lines

How it starts

The opening of the file, as written. The whole thing — 238 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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 | fp-hexagonal-architecture | fp-algebra-driven-design


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, OrderHelper.

Verb-Noun for Transformations (Pipeline-Friendly)

rawOrder
  |> validateOrderFields
  |> enrichWithCustomerData
  |> calculateOrderTotal
  |> applyDiscountRules
  |> generateOrderConfirmation

Predicate Functions Use Question-Style Names

isActiveCustomer     -- not: checkActive, activeP
hasShippingAddress   -- not: shippingAddr, addrCheck
canPlaceOrder        -- not: orderOk, validateOrderBool

When Short Names Are Acceptable

Single-letter names appropriate only in: library internals and generic utilities | lambda parameters in trivial operations | type variables | mathematical domains where convention IS domain language.

Read the full file on GitHub · 238 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 5d ago First seen · 238 lines · 20 tokens per session scan A 4b3aba348ff8

Subscribe to this mod's changes

nw-fp-usable-design is a skill published in the GitHub repository nWave-ai/nWave (610 stars, last pushed 3d ago), licensed MIT. It adds 20 tokens to every session and 2,003 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.