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 agentmods add instructions/phalves23/prompt-engineering-skill/gemini-mdgit clone --depth 1 https://github.com/PhAlves23/prompt-engineering-skillWrote 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/instructions/phalves23/prompt-engineering-skill/gemini-md)<a href="https://agentmods.dev/instructions/phalves23/prompt-engineering-skill/gemini-md"><img src="https://agentmods.dev/badge/instructions/phalves23/prompt-engineering-skill/gemini-md.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 | $0.01067 | $0.01067 |
| Opus 5 | $0.00534 | $0.00534 |
| Sonnet 5 | $0.00213 | $0.00213 |
| Haiku 4.5 | $0.00107 | $0.00107 |
Grade A, and why
prompt-engineering-skill GEMINI.md 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 4d 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 — 77 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Prompt Engineering — Gemini context
Loaded by the Gemini CLI extension (see gemini-extension.json). To use it, ask: "improve this prompt", "optimize this prompt", or paste a draft and ask to make it better.
Prompt Engineering
Turn a raw draft into a production-grade prompt. Improve the prompt, don't run it — return a rewritten version + a short changelog. Only execute the task the prompt describes if the user explicitly asks.
Operating principle
- Calibrate effort to complexity. Simple prompt → lean structural rewrite. Complex prompt (reasoning, classification, generation with criteria, agentic) → full structure. Don't over-engineer.
- If the draft is already good, say so and do the minimum. Don't invent changes to justify a rewrite.
- Default target model is Claude 4.x. If the user names another (GPT/o-series, Gemini), adjust accordingly (reasoning models do NOT want "think step by step").
- Preserve every
{{variable}}from the original. Convert negative instructions into positive ones. Add motivation to non-obvious instructions.
Workflow
- Diagnose — real intent, task type, target model, audience, output format, constraints, dynamic variables, draft weaknesses.
- Select techniques — only those that add value (see decision table).
- Rewrite in the canonical structure.
- Self-review — could a colleague with no context run this without doubt? Fix what fails.
- Deliver — optimized prompt + changelog.
Canonical structure (omit sections that don't add value)
- Role/persona — one line: who the model is + domain.
- Task + objective — what to produce + success criterion (outcome-oriented).
- Context + motivation — background + why it matters.
- Data/inputs — in XML tags. Long-context (20k+ tokens): long data at the TOP, question at the END (+up to 30% quality).
- Instructions — numbered when order matters, positive, explicit scope ("apply to ALL sections, not just the first").
- Reasoning —
<thinking>block for analytical tasks; NOT for reasoning models. - Examples (few-shot) — 3–5 diverse, in
<example>tags. Strongest lever for format/tone. - Output contract — exact format (JSON schema, XML, "result only, no preamble"). Say what to do, not what to avoid.
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.
- 4d ago First seen · 77 lines · 1,067 tokens per session scan A fb98370c7636
prompt-engineering-skill GEMINI.md is an instructions file published in the GitHub repository PhAlves23/prompt-engineering-skill (9 stars, last pushed 3mo ago), licensed MIT. It adds 1,067 tokens to every session, about $0.0053 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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