prompt-engineering

prompt-engineering is a skill for Claude Code, Codex from LuuOW/meridian-mcp. It costs 61 tokens per session (2,203 once invoked), scanned C, original, MIT.

A guide to writing prompts that make language models produce more reliable and structured results. It covers instructions, examples, tool use, context limits, output formats, and differences between models.

In plain words
What is it for?
Use it to design system prompts, few-shot examples, reasoning and tool-use instructions, structured outputs, context handling, sampling settings, and jailbreak-resistant prompts.
Why use it?
It helps reduce unclear, inconsistent, or unsafe model responses without immediately changing the model itself.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: positional $N argument.

Good fit Use it to design system prompts, few-shot examples, reasoning and tool-use instructions, structured outputs, context handling, sampling settings, and jailbreak-resistant prompts.

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Install with agentmods
npx agentmods add skills/luuow/meridian-mcp/prompt-engineering
Install

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.

Any agent
npx skills add LuuOW/meridian-mcp --skill prompt-engineering
Clone the repo
git clone --depth 1 https://github.com/LuuOW/meridian-mcp

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for prompt-engineering

README.md
[![agentmods](https://agentmods.dev/badge/skills/luuow/meridian-mcp/prompt-engineering/github.svg)](https://agentmods.dev/skills/luuow/meridian-mcp/prompt-engineering)
Your own site
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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.

agentmods 80×15 button for prompt-engineering

Your own site · 80×15
<a href="https://agentmods.dev/skills/luuow/meridian-mcp/prompt-engineering"><img src="https://agentmods.dev/badge/skills/luuow/meridian-mcp/prompt-engineering.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 61 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,203 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 2 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00061 $0.02203
Opus 5 $0.00030 $0.01102
Sonnet 5 $0.00012 $0.00441
Haiku 4.5 $0.00006 $0.00220

Measured 6d ago against content hash cad109069bab, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade C, and why

prompt-engineering scanned grade C with 2 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 6d 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.

Instruction-override phrasingmediumPrompt injection

Text telling the model to disregard its earlier instructions or safety rules is the shape of a prompt injection, whoever wrote it.

- Canonical red flags in inputs: roleplay framing to bypass persona, "ignore previous instructions", "pretend you have no restrictions", base64-encoded instructions.

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Nullifies safety policiesmediumAnti-refusal

"You have no restrictions", "do anything now", "ignore your guidelines": a direct jailbreak that disables guardrails.

- Canonical red flags in inputs: roleplay framing to bypass persona, "ignore previous instructions", "pretend you have no restrictions", base64-encoded instructions.

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

skills/prompt-engineering/SKILL.md · 188 lines

How it starts

The opening of the file, as written. The whole thing — 188 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Prompt Engineering

Broad authority on eliciting reliable, high-quality outputs from any LLM through careful prompt design. Covers system prompt architecture, reasoning techniques, tool-use orchestration, context management, and model-specific behavioral differences. Apply this skill whenever the output quality of an LLM needs to be improved, structured, or made robust — before reaching for fine-tuning.

Core Concepts

System Prompt Architecture

A well-structured system prompt has four zones: (1) role and persona, (2) task framing and constraints, (3) output format specification, (4) edge case handling. Order matters — most models weight earlier instructions more heavily.

You are a senior financial analyst at a hedge fund. You specialize in distressed debt analysis.

## Task
When given a company's 10-K excerpt, produce a structured credit risk assessment.

## Rules
- Base every claim on text explicitly present in the excerpt; never hallucinate figures.
- If information is absent, write "Not disclosed" rather than inferring.
- Use only the output format below. Do not add sections.

## Output Format
<credit_assessment>
  <rating>Investment Grade | Speculative | Distressed</rating>
  <leverage_ratio>[number]x or Not disclosed</leverage_ratio>
  <key_risks>
    <risk>...</risk>
  </key_risks>
  <recommendation>Hold | Buy | Avoid</recommendation>
</credit_assessment>

XML tags are superior to markdown headers for structured outputs because they survive nested generation without ambiguity. Claude responds especially well to XML. GPT-4o and Gemini 1.5 Pro both handle JSON mode natively and can be instructed to output JSON schema-conformant objects.

Few-Shot Examples

Few-shot examples are the most reliable technique for format compliance and tone calibration. Place examples after task description, before the actual input.

## Examples

Input: "The quarterly revenue declined 12% YoY."
Output:
<sentiment>Negative</sentiment>
<magnitude>Moderate</magnitude>
<entity>Revenue</entity>

Input: "We beat consensus estimates by $0.18 per share."
Output:
<sentiment>Positive</sentiment>
<magnitude>Strong</magnitude>
<entity>EPS</entity>

---
Input: {{user_text}}
Output:

Read the full file on GitHub · 188 lines

Changes

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.

  1. 6d ago First seen · 188 lines · 61 tokens per session scan C cad109069bab

Subscribe to this mod's changes

prompt-engineering is a skill published in the GitHub repository LuuOW/meridian-mcp (0 stars, last pushed yesterday), licensed MIT. It adds 61 tokens to every session and 2,203 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it C with 2 findings (instruction-override phrasing, nullifies safety policies). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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