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 onatm/agent-skills --skill docs-feature-designgit clone --depth 1 https://github.com/onatm/agent-skillsWrote 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/onatm/agent-skills/docs-feature-design)<a href="https://agentmods.dev/skills/onatm/agent-skills/docs-feature-design"><img src="https://agentmods.dev/badge/skills/onatm/agent-skills/docs-feature-design.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00037 | $0.00604 |
| Opus 5 | $0.00018 | $0.00302 |
| Sonnet 5 | $0.00007 | $0.00121 |
| Haiku 4.5 | $0.00004 | $0.00060 |
Grade A, and why
docs-feature-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 7d 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 — 66 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Docs Feature Design
Maintain docs that explain what a feature does and why it matters, not how it is implemented. A single component or service may support multiple features, so keep technical design out of feature docs and link it separately when needed.
Resource Map
- Use
assets/doc-starters/feature-doc.mdwhen creating or substantially rewriting a doc indocs/features/. - Read
references/feature-example.mdwhen you need a worked example of the expected behavior-focused depth.
When to Use
- New feature definition or major feature revision
- Changes to user-visible behavior, primary flows, goals, rules, or constraints
- Updates to product scope, supported actors, or expected outcomes
- Feature docs that should stay understandable without reading implementation details
Do Not Use
- API, schema, runtime, deployment, or internal control-flow detail that belongs in
docs-components-design - System topology or domain architecture that belongs in
docs-architecture
Workflow
- Identify the feature, audience, and existing doc path.
- Default location is
docs/features/ - Reuse an existing feature doc when one already exists
- Capture behavior-level content only.
- User problem and goals
- Primary actors and entry points
- Main flows, states, and business rules
- User-visible edge cases, constraints, and outcomes
- Non-Goals, Audience / Actors, and Open Questions are optional — omit them when they don't add value for the feature
- "User-Facing Behavior" (flat bullet list) is a valid simpler alternative to formal numbered Primary Flows for straightforward features
- Move technical detail out.
- If the draft starts describing APIs, schema, queues, retries, deployment, or internal implementation, link or create the relevant component design doc instead
- Keep cross-links aligned.
- Link to relevant architecture and component docs
- Do not duplicate their content inside the feature doc
- Verify the doc against the current product behavior.
- The described flows and rules match what the feature actually does
- The audience can understand the feature without technical context
What ships with it
3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 7d ago First seen · 66 lines · 37 tokens per session scan A 7eb8b30df53d
docs-feature-design is a skill published in the GitHub repository onatm/agent-skills (7 stars, last pushed 1mo ago), licensed MIT. It adds 37 tokens to every session and 604 once invoked, about $0.0002 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 2026-08-31.
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