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 bdfinst/agentic-dev-team --skill design-it-twicegit clone --depth 1 https://github.com/bdfinst/agentic-dev-teamWrote 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/bdfinst/agentic-dev-team/design-it-twice)<a href="https://agentmods.dev/skills/bdfinst/agentic-dev-team/design-it-twice"><img src="https://agentmods.dev/badge/skills/bdfinst/agentic-dev-team/design-it-twice/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/bdfinst/agentic-dev-team/design-it-twice"><img src="https://agentmods.dev/badge/skills/bdfinst/agentic-dev-team/design-it-twice.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 | $0.00093 | $0.00864 |
| Opus 5.5 | $0.00037 | $0.00346 |
| Sonnet 5.5 | $0.00019 | $0.00173 |
| Haiku 4.5 | $0.00009 | $0.00086 |
Grade A, and why
design-it-twice 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 — 92 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Design It Twice
Overview
Your first design idea is rarely your best. This skill generates multiple radically different interface designs for a module by dispatching parallel sub-agents with divergent constraints, then compares them so the user can make an informed choice. Based on "Design It Twice" from John Ousterhout's A Philosophy of Software Design.
This skill is about interface shape, not implementation. Don't write code — design the contract.
When to Use
- Designing a new module, service, or API boundary
- Refactoring an existing interface that feels wrong
- Any time there's a non-obvious choice about how to expose functionality
- When the Architect agent identifies a new module boundary during planning
Process
1. Gather Requirements
Before designing, understand the constraints:
- What problem does this module solve?
- Who are the callers? (other modules, external users, tests)
- What are the key operations?
- What should be hidden inside vs exposed?
- Any hard constraints? (performance, compatibility, existing patterns in the codebase)
Explore the codebase to find existing patterns and conventions. Ask the user only for what you can't determine from the code.
2. Generate Designs (Parallel Sub-Agents)
Spawn 3+ sub-agents simultaneously using the Agent tool. Each must produce a radically different approach — not variations on a theme.
Assign each agent a different design constraint:
| Agent | Constraint | Optimizes for |
|---|---|---|
| 1 | "Minimize the interface — aim for 1-3 methods max" | Simplicity, deep module |
| 2 | "Maximize flexibility — support many use cases and extension" | Generality, future-proofing |
| 3 | "Optimize for the most common caller — make the default case trivial" | Ergonomics, productivity |
| 4 | (optional) "Design around ports & adapters for cross-boundary deps" | Testability, isolation |
Each sub-agent produces:
- Interface signature — types, methods, parameters
- Usage example — how a real caller would use it
- What it hides — complexity kept internal
- Trade-offs — what you gain and what you give up
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 · 92 lines · 93 tokens per session scan A b84df5de5b6d
design-it-twice is a skill published in the GitHub repository bdfinst/agentic-dev-team (295 stars, last pushed 4d ago), licensed MIT. It adds 93 tokens to every session and 864 once invoked, about $0.0004 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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