prompt-engineer

prompt-engineer is an agent for Claude Code from GoogilyBoogily/googilyboogily-claude-power-tools. It costs 36 tokens per session (367 once invoked), scanned A, original, MIT.

A specialist for designing and improving instructions given to language models. It covers prompt structure, examples, evaluation methods, testing, and managing prompts in production.

In plain words
What is it for?
Use it to design prompts, add few-shot examples, create evaluation frameworks, and optimise prompt behaviour.
Why use it?
It helps make model instructions clearer, more reliable, and easier to test across different models and use cases.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: model in frontmatter.

Part of the ai-agents plugin — 3 agents shipped together

Good fit Use it to design prompts, add few-shot examples, create evaluation frameworks, and optimise prompt behaviour.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/googilyboogily/googilyboogily-claude-power-tools/prompt-engineer
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.

Clone the repo
git clone --depth 1 https://github.com/GoogilyBoogily/googilyboogily-claude-power-tools

Made for: Claude Code.

Or install ai-agents, the plugin that ships this one along with the rest of its 3 agents.

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-engineer

README.md
[![agentmods](https://agentmods.dev/badge/agents/googilyboogily/googilyboogily-claude-power-tools/prompt-engineer/github.svg)](https://agentmods.dev/agents/googilyboogily/googilyboogily-claude-power-tools/prompt-engineer)
Your own site
<a href="https://agentmods.dev/agents/googilyboogily/googilyboogily-claude-power-tools/prompt-engineer"><img src="https://agentmods.dev/badge/agents/googilyboogily/googilyboogily-claude-power-tools/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.

agentmods 80×15 button for prompt-engineer

Your own site · 80×15
<a href="https://agentmods.dev/agents/googilyboogily/googilyboogily-claude-power-tools/prompt-engineer"><img src="https://agentmods.dev/badge/agents/googilyboogily/googilyboogily-claude-power-tools/prompt-engineer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 36 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 367 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 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 $0.00036 $0.00367
Opus 5 $0.00018 $0.00183
Sonnet 5 $0.00007 $0.00073
Haiku 4.5 $0.00004 $0.00037

Measured 12d ago against content hash 9d9aa285e85a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

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 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.

plugins/ai-agents/agents/prompt-engineer.md · 45 lines

What it actually says

Prompt Engineer

Expert in designing, testing, and optimizing prompts for large language models across all use cases and model families.

Step 0: Route or Stay

Before starting, verify the task is within scope. Delegate otherwise:

Signal Route to
System-level LLM architecture decisions (RAG, serving, pipelines) llm-architect
Infrastructure or model serving concerns devops-expert
AI SDK integration or API usage patterns ai-sdk-expert
General code quality or refactoring refactoring-expert

STOP Conditions

  • Task requires system-level LLM architecture changes — hand to llm-architect
  • Problem is infrastructure or serving, not prompt content — stop
  • Prompt is optimized and remaining work is application integration — stop
  • Focus on prompt content and structure — not infrastructure or serving

Methodology

  1. Understand the target model, use case, and success criteria
  2. Analyze existing prompts for failure modes and improvement opportunities
  3. Design or refine prompts using proven patterns (chain-of-thought, few-shot, structured output)
  4. Establish evaluation criteria and test against edge cases

Approach

  • Minimize token usage while maintaining output quality
  • Use structured outputs (JSON, XML) when downstream parsing is needed
  • Always consider failure modes: what happens when the model misunderstands?
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. 12d ago First seen · 45 lines · 36 tokens per session scan A 9d9aa285e85a

Subscribe to this mod's changes

prompt-engineer is an agent published in the GitHub repository GoogilyBoogily/googilyboogily-claude-power-tools (2 stars, last pushed 4mo ago), licensed MIT. It adds 36 tokens to every session and 367 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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