design-interface

A design exercise that creates several different shapes for a software interface before one is chosen.

In plain words
What is it for?
It helps design APIs and module boundaries by gathering requirements, producing multiple contrasting options, and comparing their trade-offs.
Why use it?
It reduces the risk of committing to the first design without comparing its complexity, user experience, flexibility, and performance.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/danielvm-git/bigpowers/design-interface
Any agent
npx skills add danielvm-git/bigpowers --skill design-interface
Clone the repo
git clone --depth 1 https://github.com/danielvm-git/bigpowers

Made for: Claude Code, Codex.

Per session 61 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 772 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00061 $0.00772
Opus 5 $0.00030 $0.00386
Sonnet 5 $0.00012 $0.00154
Haiku 4.5 $0.00006 $0.00077

Measured 2d ago against content hash d362cf553894, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

design-interface 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 2d 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.

.cline/skills/design-interface/SKILL.md · 98 lines

How it starts

The opening of the file, as written. The whole thing — 98 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Design Interface

Based on "Design It Twice" from "A Philosophy of Software Design": your first idea is unlikely to be the best. Generate multiple radically different designs, then compare.

HARD GATE — Multiple design options must be explored. Do NOT settle on first idea. Compare trade-offs (UX, complexity, extensibility, performance) before committing.

Workflow

1. Gather Requirements

Before designing, understand:

  • What problem does this module solve?
  • Who are the callers? (other modules, external users, tests)
  • What are the key operations?
  • Any constraints? (performance, compatibility, existing patterns)
  • What should be hidden inside vs exposed?

Ask: "What does this module need to do? Who will use it?"

2. Generate Designs (Parallel Sub-Agents)

Spawn 3+ sub-agents simultaneously using Task tool. Each must produce a radically different approach.

Prompt template for each sub-agent:

Design an interface for: [module description]

Requirements: [gathered requirements]

Constraints for this design: [assign a different constraint to each agent]
- Agent 1: "Minimize method count - aim for 1-3 methods max"
- Agent 2: "Maximize flexibility - support many use cases"
- Agent 3: "Optimize for the most common case"
- Agent 4: "Take inspiration from [specific paradigm/library]"

Output format:
1. Interface signature (types/methods)
2. Usage example (how caller uses it)
3. What this design hides internally
4. Trade-offs of this approach

3. Present Designs

Show each design with:

  1. Interface signature — types, methods, params
  2. Usage examples — how callers actually use it in practice
  3. What it hides — complexity kept internal

Present designs sequentially so user can absorb each approach before comparison.

4. Compare Designs

After showing all designs, compare them on:

  • Interface simplicity: fewer methods, simpler params
  • General-purpose vs specialized: flexibility vs focus
  • Implementation efficiency: does shape allow efficient internals?
  • Depth: small interface hiding significant complexity (good) vs large interface with thin implementation (bad)
  • Ease of correct use vs ease of misuse

Read the full file on GitHub · 98 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. 2d ago First seen · 98 lines · 61 tokens per session scan A d362cf553894

Subscribe to this mod's changes

design-interface is a skill published in the GitHub repository danielvm-git/bigpowers (156 stars, last pushed 25d ago), licensed MIT. It adds 61 tokens to every session and 772 once invoked, about $0.0003 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 2026-08-30.

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