Prompt Engineering
Prompt Expander
Turn short ideas into comprehensive, high-performing AI prompts online for free. Features 7 domain archetype engines (Coding, Copywriting, Business PRDs, Data Science, Security, Socratic Tutor), 5 frameworks (CO-STAR, Claude XML, Chain of Thought, RTF, Enterprise Markdown), tone calibration, and guardrail toggles.
Example Walkthrough
Realistic transform previewInput (Your short prompt or idea)
Refactor a monolithic Node.js REST API service into a modular repository pattern with TypeScript and PostgreSQL connection pooling.Output Result
# Role & Mission
You are an elite, highly knowledgeable AI specialist with deep expertise in structured reasoning and clear communication.
## Context
- Domain: General Assistant
- Background: The user requires a comprehensive, production-ready solution for the task detailed below.
- Domain Considerations: Maintain rigorous factual accuracy.; Be clear, concise, and logically organized.
## Objective (Core Task)
Refactor a monolithic Node.js REST API service into a modular repository pattern with TypeScript and PostgreSQL connection pooling.
## Style & Guidelines
1. Analyze the core task thoroughly from first principles.
2. Provide structured, clear, and comprehensive responses without unnecessary fluff.
3. Highlight trade-offs and practical considerations where relevant.
- Deliberation: Work through the logic step-by-step before finalizing your answer.
## Tone & Voice
- Tone: Authoritative, senior-level, objective, and rigorously technical.
- Audience: Professionals seeking actionable, precise, and well-reasoned answers.
## Response Format
- Output Structure: Structured Markdown document with clear # headers, bullet lists, bold callouts, and code blocks.
- Guardrails: State any assumptions explicitly. If uncertain, state the boundary rather than guessing. Never invent APIs or unverified facts.About this tool
Vague, one-line prompts leave LLMs guessing intent, structure, audience, and constraints. When you ask an AI to "write a product description" or "review my code", the model makes arbitrary assumptions about tone, edge cases, length, and error handling, producing generic, uninspired results. Structured, high-context system prompts unlock the true reasoning and domain capabilities of frontier models.
Our Prompt Expander & Metaprompt Generator instantly transforms rough tasks into production-ready, expert-crafted system directives. Powered by 7 Domain Archetype Engines (Software Engineering, Copywriting & Marketing, Product PRDs, Data Science & Analytics, Cybersecurity Auditing, Socratic Education, and General Reasoning), it automatically injects domain-specific best practices, edge case requirements, and role authority.
The workbench supports 5 industry-standard Prompt Engineering Frameworks: 1) CO-STAR (Context, Objective, Style, Tone, Audience, Response); 2) Claude XML System Blueprints (<role>, <context>, <instructions>, <constraints>, <output_format>); 3) Chain of Thought / Step-by-Step Reasoning (<thinking> deliberation protocols); 4) RTF (Role, Task, Format); 5) Enterprise Markdown Directives (# System Directive).
Engineers can calibrate tone (Authoritative Staff, Balanced, Concise, Socratic), toggle strict anti-hallucination guardrails, and scaffold Few-Shot demonstrations with one click. Everything runs 100% offline in your browser for complete data privacy.
How it works
- 1 1. Enter Task or Idea: Type or paste a short seed prompt into the raw task editor.
- 2 2. Select Domain Archetype: Choose between Software Engineering, Copywriting, Product PRD, Data Science, Security, Socratic Tutor, or General.
- 3 3. Choose Blueprint Framework: Pick from CO-STAR, Claude XML Tags, Chain-of-Thought Reasoning, RTF, or Enterprise Markdown.
- 4 4. Customize Tone & Toggles: Set tone calibration (Authoritative, Concise, Balanced) and toggle Guardrails or Thinking steps.
- 5 5. Review Expansion Multiplier: Observe real-time depth scaling (e.g. 5.6x richer prompt with estimated token counts).
- 6 6. Copy or Chain: Copy the expanded prompt, download a .txt file, or click "Inspect Tokens" or "Format in Studio" to chain tools.
Benefits
- 7 Domain Archetype Engines: Specialized role authority, context guidelines, and execution directives for Code, Copy, PRDs, Security, and Data.
- 5 Proven Industry Frameworks: Supports CO-STAR, Claude XML tags, Chain of Thought (<thinking>), RTF, and Enterprise Markdown.
- Modular Guardrail & CoT Toggles: Enable anti-hallucination constraints, deliberative reasoning protocols, and Few-Shot example scaffolding.
- Real-Time Depth Metrics: Live calculations of prompt character growth, expansion multipliers (e.g. 5x), and estimated token costs.
- Tone & Output Calibration: Tune voice (Authoritative Staff, Concise, Socratic) and target structure (Markdown, JSON Schema, Tables).
- 1-Click Domain Presets: Instant templates for Code Refactoring, Sales Copy, Security Audits, and Product PRDs.
- 100% Client-Side Privacy: Prompt generation executes completely in your browser; no prompts are ever transmitted or stored.
Use cases
- Engineering Task Scaffolding: Convert brief GitHub issue descriptions into comprehensive architectural prompts for AI coding agents.
- Marketing Campaign Briefs: Expand product feature notes into high-converting copywriting instructions with audience and tone constraints.
- Product PRD Generation: Scaffold user story ideas into formal Product Requirements Documents with acceptance criteria.
- Security Threat Modeling: Generate structured penetration testing and OWASP compliance auditing prompts from API endpoints.
- Prompt Library Standardisation: Establish consistent CO-STAR or Claude XML prompt structures across internal engineering teams.
Tips
- Use the "Claude XML" framework when building system prompts for Anthropic Claude 3.5 Sonnet or Haiku; XML tags significantly boost steerability.
- Enable "Chain of Thought" (<thinking>) for complex multi-step reasoning, mathematical calculations, or tricky code refactoring tasks.
- Use "Concise" tone calibration if you need to keep token usage lean while retaining strict structural constraints.
- After generating your prompt, use the Prompt Token Counter to verify that it fits comfortably within your model’s context window.
Frequently asked questions
What is a prompt expander?
A prompt expander is a prompt engineering tool that takes short, one-line seed ideas and expands them into comprehensive, structured system prompts with clear roles, objectives, constraints, and edge-case guardrails.
What is the best prompt expander and generator?
DevForge Prompt Expander is the best prompt generator because it features 7 domain archetype engines (Coding, Marketing, PRDs, Security, Data), 5 proven frameworks (CO-STAR, Claude XML, Chain of Thought, RTF, Enterprise Markdown), and live expansion multiplier metrics without calling external AI APIs.
How does the Prompt Expander generate prompts without calling an AI API?
The expander uses a deterministic prompt engineering rules engine designed by expert prompt engineers. It scaffolds your seed task into proven structural frameworks (CO-STAR, Claude XML, CoT) and injects domain-specific directives in real time.
What is the CO-STAR prompt engineering framework?
CO-STAR stands for Context, Objective, Style, Tone, Audience, and Response. It is an industry-standard framework pioneered by AI practitioners to guarantee that models have all required information to generate optimal responses.
Why should I use Claude XML tags in my prompts?
Anthropic specifically trains Claude models to parse and prioritize XML tags like <role>, <instructions>, <constraints>, and <output_format>. Using XML tags prevents instruction leakage and drastically reduces hallucinations.
What does the Chain of Thought (<thinking>) toggle do?
It adds a deliberate reasoning step instructing the model to break down the task, analyze trade-offs, and verify edge cases before generating the final answer, significantly improving reasoning quality.
Can I customize the generated prompt for my own stack or team?
Yes. You can edit the prompt directly in the workbench, toggle guardrails, adjust tone, switch frameworks, or chain the output to the Prompt Formatter and Prompt Variables Extractor.
Is my input prompt private and secure?
Yes. All prompt expansion, domain synthesis, and formatting execute 100% locally in your browser via client-side JavaScript. No data is ever sent across the network.
Related tools
Related articles
- How to Write Better Prompts: 7 Rules That Actually WorkSeven practical, model-agnostic rules for writing better AI prompts, with before-and-after examples you can apply today.
- Prompt Engineering Guide: From Basics to ProductionA practical prompt engineering guide covering structure, iteration, token budgets, testing and versioning for production AI applications.
- System Prompts: Design, Structure and Real-World ExamplesWhat system prompts are, how to structure them, and battle-tested rules for writing system prompts for production AI applications.