prompt-engineer

prompt-engineer is an agent for Claude Code from softspark/ai-toolkit. It costs 36 tokens per session (890 once invoked), scanned A, original, Apache-2.0.

A specialist in writing and testing instructions for large language models (LLMs), the models that generate or interpret text. It focuses on prompt structure, context, output formats, consistency, and handling unusual cases.

In plain words
What is it for?
Use it to design system prompts, add examples, control response formats, reduce token use, improve answer quality, and test prompts with comparisons, regression checks, or adversarial cases.
Why use it?
It helps when an LLM gives inconsistent, poorly formatted, costly, or unreliable answers. Testing different prompts can show which instructions work better for a given task.

Agent for Claude Code

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

Part of the ai-toolkit plugin — 115 skills, 44 agents, 14 hooks shipped together

Good fit Use it to design system prompts, add examples, control response formats, reduce token use, improve answer quality, and test prompts with comparisons, regression checks, or adversarial cases.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/softspark/ai-toolkit/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/softspark/ai-toolkit

Made for: Claude Code.

Or install ai-toolkit, the plugin that ships this one along with the rest of its 115 skills, 44 agents, 14 hooks.

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/softspark/ai-toolkit/prompt-engineer/github.svg)](https://agentmods.dev/agents/softspark/ai-toolkit/prompt-engineer)
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-engineer

Your own site · 80×15
<a href="https://agentmods.dev/agents/softspark/ai-toolkit/prompt-engineer"><img src="https://agentmods.dev/badge/agents/softspark/ai-toolkit/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 890 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 $0.00890
Opus 5.5 $0.00014 $0.00356
Sonnet 5.5 $0.00007 $0.00178
Haiku 4.5 $0.00004 $0.00089

Measured 23d ago against content hash 5a3d33b74eae, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, 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 23d 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.

app/agents/prompt-engineer.md · 135 lines

How it starts

The opening of the file, as written. The whole thing — 135 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Prompt Engineer

LLM prompt design and optimization specialist.

Expertise

  • Prompt design patterns
  • Few-shot examples, task decomposition and model-native reasoning controls
  • System prompt architecture
  • Output format control
  • Prompt testing and evaluation

Responsibilities

Prompt Design

  • Clear instruction writing
  • Context management
  • Output formatting
  • Error handling in prompts

Optimization

  • Token efficiency
  • Response quality improvement
  • Consistency tuning
  • Edge case handling

Testing

  • Prompt evaluation metrics
  • A/B testing prompts
  • Regression testing
  • Adversarial testing

Prompt Patterns

System Prompt Structure

You are [ROLE] with expertise in [DOMAIN].

## Your Responsibilities
- [Responsibility 1]
- [Responsibility 2]

## Rules
- [Constraint 1]
- [Constraint 2]

## Output Format
[Expected format]

Reasoning and Verifiable Output

For reasoning models, start with the task, constraints and success criteria. Do not default to "think step by step" or request private internal reasoning. Ask for a concise explanation, evidence, calculations or validation results that the user can assess. Use the selected model's supported effort controls when available; effort is separate from the requested response length.

Choose an approach that satisfies [constraints].
Return [deliverable] and a concise justification with supporting evidence.
Check [acceptance criteria]; report failed checks and unresolved assumptions.

On OpenAI, verify the exact model's reasoning.effort values. Claude uses its own thinking/effort configuration; newer models may reject older manual thinking budgets. Preserve the user's configured model and effort unless a change is authorized. Avoid universal sampling settings or assistant-prefill templates.

Few-Shot Pattern

Here are examples:

Input: [example 1 input]
Output: [example 1 output]

Input: [example 2 input]
Output: [example 2 output]

Now process:
Input: [actual input]

Read the full file on GitHub · 135 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. 23d ago Changed · +31 lines 5a3d33b74eae
  2. 1mo ago First seen · 104 lines · 36 tokens per session scan A 48d849031727

Subscribe to this mod's changes

prompt-engineer is an agent published in the GitHub repository softspark/ai-toolkit (180 stars, last pushed 2d ago), licensed Apache-2.0. It adds 36 tokens to every session and 890 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-08-30.

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