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 alphacornutum/layercake --skill prompt-engineeringgit clone --depth 1 https://github.com/alphacornutum/layercakeWrote 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/alphacornutum/layercake/prompt-engineering)<a href="https://agentmods.dev/skills/alphacornutum/layercake/prompt-engineering"><img src="https://agentmods.dev/badge/skills/alphacornutum/layercake/prompt-engineering/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/alphacornutum/layercake/prompt-engineering"><img src="https://agentmods.dev/badge/skills/alphacornutum/layercake/prompt-engineering.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 | $0.00171 | $0.04030 |
| Opus 5.5 | $0.00068 | $0.01612 |
| Sonnet 5.5 | $0.00034 | $0.00806 |
| Haiku 4.5 | $0.00017 | $0.00403 |
Grade B, and why
prompt-engineering scanned grade B with 1 finding 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 2d 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.
Asks the agent to reveal its instructionsmediumSystem prompt leakage
Directions to print, repeat or translate the system prompt extract configuration the operator did not intend to expose.
- **Golden rule**: show your prompt to a colleague with no context. If they'd be confused, the model will be too. How it starts
The opening of the file, as written. The whole thing — 123 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Prompt Engineering
A workflow and toolbox for writing prompts that steer modern LLMs reliably — system prompts, slash commands, skills, rules, agent personas, and one-off queries.
Bundled references (load on demand)
references/snippets.md— read when you need a copy-paste prompt fragment for a recurring concern: anti-overengineering, parallel tool calls, default-to-action / do-not-act, investigate-before-answering, code-review coverage, frontend aesthetics, frontend variety / propose-options, subagent control, persistence across context windows, multi-context state tracking, reversibility/safety, verbosity, long-document grounding, keep-going stop rules, and the GPT-6 Astra steering set. ~25 vetted blocks.references/metaprompting.md— read when a prompt under-performs and the cause is unclear: full metaprompting template, filtering procedure for the model's suggestions, when to use vs. skip.references/agent-persona.md— read when designing or auditing the system prompt of an autonomous agent: identity, autonomy posture, tool-use rules, editing constraints, full Friendly and Pragmatic personality blocks, final-message format, plan discipline.
Workflow
- Define success first — write one sentence: what must the output be, and for whom. Define the eval criteria before the prompt. If you can't, the prompt isn't ready.
- Draft with the minimal components — Objective + Instructions + (if needed) Context, Role, Format, Examples. Add a component only when you can justify it.
- Build a test set — 3+ diverse inputs: happy path, edge cases, malformed input. Tiny is fine; some signal beats none.
- Run and grade — code-grade where possible (JSON/regex/Python parse, length, keyword presence), model-grade for quality, human-grade for nuance. Always demand reasoning + score from a model grader, not a bare score.
- Diagnose before patching — name the cause (ambiguous scope? missing context? conflicting instruction? wrong format?). Fix the cause, not the symptom. When the cause is unclear, run metaprompting (see
references/metaprompting.md). - Change one thing at a time — otherwise you won't know what worked.
- Iterate — re-run the same test set, compare versions; stop when stable across all of them, not when "looks good once".
- Pin and version — for production, pin to a specific model snapshot (e.g.,
claude-opus-5-5,gpt-6-astra) and re-run evals when upgrading — a model upgrade shifts behaviour silently and your evals are the only signal.
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.
- 2d ago Changed 87bb56e80da2
- 20d ago First seen · 123 lines · 171 tokens per session scan B 7abbefd2748a
prompt-engineering is a skill published in the GitHub repository alphacornutum/layercake (0 stars, last pushed 3d ago), licensed MIT. It adds 171 tokens to every session and 4,030 once invoked, about $0.0007 per session on Opus 5.5. A static security scan graded it B with 1 finding (asks the agent to reveal its instructions). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-26.
Other skills, from other repositories
after-effects-scripting
Drive a running After Effects instance directly from the shell to build, edit and render motion graphics — no MCP, plugin or panel required. Use whenever the user wants Claude to work inside After Effects: building animations, title sequences, logo stings, UI/product motion, data visualisations, or fixing an existing…
vox-director
Turn ONE topic into a finished Vox-style paper-collage explainer / ad video, end to end on the Atlas Cloud API + local ffmpeg — script, collage keyframes, motion, voice-over, music, captions, all automated. Use this whenever the user wants a "Vox style" video, a paper/torn-paper collage animation, a "motion collage"…
style-guide
Help a motion designer capture their house style — palette, type, motion and layout — into the house-style.md file that sits next to their After Effects project and shapes everything built afterwards. Load when the user asks to create, edit or review their style guide, when they say work does not look like theirs, or…
flue
Let agents control software, like Adobe Photoshop, Illustrator, After Effects, Premiere, Autodesk 3DS Max, Blender, Unity, Houdini, and Microsoft Office.
hyperframes-product-launch-video
Create product launch videos from a URL, brief, or script using HyperFrames (HTML→MP4). Use when the user wants a product launch video, site tour, social clip featuring a product's own visuals, or marketing/promoting a product. Up to 3 min (sweet spot 30-90s). Teaches the HyperFrames production loop: plan → write HTML…
hyperframes-motion-graphics
Create short, unnarrated, design-led motion graphics (under 10s) using HyperFrames. Use when the user wants kinetic type, stat/chart hits, logo stings, lower-thirds, animated tweets/headlines, or transparent overlay motion graphics. MP4 or transparent overlay output. Teaches seek-safe keyframe authoring and the 2-3…