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.
npx skills add softspark/ai-toolkit --skill design-an-interfacegit clone --depth 1 https://github.com/softspark/ai-toolkitWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/softspark/ai-toolkit/design-an-interface)<a href="https://agentmods.dev/skills/softspark/ai-toolkit/design-an-interface"><img src="https://agentmods.dev/badge/skills/softspark/ai-toolkit/design-an-interface/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/softspark/ai-toolkit/design-an-interface"><img src="https://agentmods.dev/badge/skills/softspark/ai-toolkit/design-an-interface.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00036 | $0.00835 |
| Opus 5.5 | $0.00014 | $0.00334 |
| Sonnet 5.5 | $0.00007 | $0.00167 |
| Haiku 4.5 | $0.00004 | $0.00084 |
Grade A, and why
design-an-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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 106 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Design an Interface
$ARGUMENTS
Generate 3+ radically different interface designs using parallel sub-agents, then compare. Based on "Design It Twice" from "A Philosophy of Software Design."
Usage
/design-an-interface [module or interface to design]
What This Command Does
- Gathers requirements and constraints
- Spawns 3+ parallel sub-agents with different design constraints
- Presents each design with signatures, usage examples, and trade-offs
- Compares on simplicity, depth, efficiency, and correctness
- Synthesizes best elements into final recommendation
Process
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?
2. Generate Designs (Parallel Sub-Agents)
Spawn 3+ sub-agents simultaneously using Agent tool. Each gets a radically different constraint:
| Agent | Constraint |
|---|---|
| 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 a specific paradigm/library |
Each agent outputs:
- Interface signature (types/methods)
- Usage example (how caller uses it)
- What this design hides internally
- Trade-offs of this approach
3. Present Designs
Show each design sequentially so user can absorb each approach before comparison:
- Interface signature — types, methods, params
- Usage examples — how callers actually use it
- What it hides — complexity kept internal
4. Compare Designs
Compare in prose (not tables) on:
| Criterion | Description |
|---|---|
| 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 |
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.
- 1mo ago First seen · 106 lines · 36 tokens per session scan A 25822fac537f
design-an-interface is a skill published in the GitHub repository softspark/ai-toolkit (180 stars, last pushed yesterday), licensed Apache-2.0. It adds 36 tokens to every session and 835 once invoked, about $0.0001 per session on Opus 5.5. 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.
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