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 lvcoi/solidJSkills --skill system-prompt-engineergit clone --depth 1 https://github.com/lvcoi/solidJSkillsWrote 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/lvcoi/solidjskills/system-prompt-engineer)<a href="https://agentmods.dev/skills/lvcoi/solidjskills/system-prompt-engineer"><img src="https://agentmods.dev/badge/skills/lvcoi/solidjskills/system-prompt-engineer/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/lvcoi/solidjskills/system-prompt-engineer"><img src="https://agentmods.dev/badge/skills/lvcoi/solidjskills/system-prompt-engineer.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00036 | $0.00163 |
| Opus 5 | $0.00018 | $0.00081 |
| Sonnet 5 | $0.00007 | $0.00033 |
| Haiku 4.5 | $0.00004 | $0.00016 |
Grade A, and why
system-prompt-engineer 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 9d 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.
What it actually says
System Prompt Engineer
Build high-clarity prompts that reduce ambiguity and enforce policy.
Authoring Flow
- Declare role and domain context.
- List non-negotiable constraints and precedence.
- Specify tool usage and prohibited actions.
- Define required output format and evidence rules.
- Add fallback behavior for unknowns and blocked operations.
Validation
- Test prompt against at least three realistic scenarios.
- Verify precedence handling under conflicting instructions.
- Confirm output is structurally consistent.
References
Load references/prompt-audit.md to perform prompt quality review.
What ships with it
1 file 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.
- 9d ago First seen · 27 lines · 36 tokens per session scan A 23803e1f881f
system-prompt-engineer is a skill published in the GitHub repository lvcoi/solidJSkills (10 stars, last pushed 6mo ago), licensed MIT. It adds 36 tokens to every session and 163 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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