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 timwukp/agent-skills-best-practice --skill security-story-writinggit clone --depth 1 https://github.com/timwukp/agent-skills-best-practiceWrote 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/timwukp/agent-skills-best-practice/security-story-writing)<a href="https://agentmods.dev/skills/timwukp/agent-skills-best-practice/security-story-writing"><img src="https://agentmods.dev/badge/skills/timwukp/agent-skills-best-practice/security-story-writing/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/timwukp/agent-skills-best-practice/security-story-writing"><img src="https://agentmods.dev/badge/skills/timwukp/agent-skills-best-practice/security-story-writing.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 | $0.00122 | $0.01042 |
| Opus 5 | $0.00061 | $0.00521 |
| Sonnet 5 | $0.00024 | $0.00208 |
| Haiku 4.5 | $0.00012 | $0.00104 |
Grade A, and why
security-story-writing 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 12d 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 — 88 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Security Story Writing
Convert security work — threats from a threat model, SAST/DAST findings, pen-test results, compliance controls — into stories a Scrum team can estimate, schedule, and verify like any other backlog item.
Story Types
Pick the right shape for the input:
- Security control story — a new protective capability (rate limiting, input validation, audit logging). Written from the system's or security role's perspective.
- Vulnerability remediation story — fixing a specific finding. Must reference the finding ID and include a regression test criterion.
- Feature story with security criteria — a normal feature story that gains explicit security acceptance criteria. Use when security is a property of the feature, not separate work.
- Compliance story — implementing a named control from a framework (PCI-DSS requirement, MAS TRM section). Must cite the specific control number so auditors can trace it.
Templates
Security control story
### [ID] [Control title]
**As** [the system / a security role], **I want** [security control], **so that** [risk is mitigated].
**Threat:** [STRIDE category or threat-model reference]
**Compliance:** [framework + control number, if applicable]
#### Acceptance Criteria
- Given [precondition], when [attack vector attempted], then [system prevents/detects and logs/alerts]
- Given [precondition], when [normal operation], then [control is active without breaking the user flow]
#### Security Regression Test
- Automated test proving [the attack] fails, runs in CI from this sprint onward
Vulnerability remediation story
### [ID] Fix: [finding title]
**Finding:** [scanner/report ID, severity, CVSS if available]
**Affected:** [component, endpoint, or file]
#### Acceptance Criteria
- Given the conditions in the finding, when [the exploit is attempted], then it fails
- The fix introduces no functional regression in [affected flows]
- A regression test reproducing the original exploit is added to CI
What ships with it
2 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.
- 12d ago First seen · 88 lines · 122 tokens per session scan A b8a1351bcc8f
security-story-writing is a skill published in the GitHub repository timwukp/agent-skills-best-practice (10 stars, last pushed 2d ago), licensed MIT. It adds 122 tokens to every session and 1,042 once invoked, about $0.0006 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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