Introduction

As generative AI becomes part of everyday life, a new skill has quietly emerged: learning how to ask better questions.

You may have heard the term prompt engineering and assumed it was only for engineers or AI experts. In reality, it's much simpler. Prompting is just the practice of communicating clearly with a machine so it can give you a useful, relevant answer.

Early AI interactions were often playful or basic — "Tell me a joke about a cat." But as tools like ChatGPT and Gemini have grown more capable, the gap between a vague prompt and a great result has widened. Simply asking a question is no longer enough. AI works best when it's given context, direction, and clear boundaries.

That's where structured frameworks like COSTAR come in.

Why Prompt Structure Matters

Modern AI systems are powerful, but they are not mind readers. When instructions are unclear, the output tends to be generic. When instructions are precise, the results feel focused, thoughtful, and surprisingly human.

Prompt design has even become a competitive discipline. In Singapore's first GPT-4 prompt engineering competition, participants were judged on how effectively they could guide AI toward high-quality results. Frameworks like COSTAR stood out by proving that how you ask matters just as much as what you ask.

What Is COSTAR?

COSTAR is a simple checklist for building better prompts. Each letter represents a key element that helps the AI understand exactly what you need.

• C — Context
• O — Objective
• S — Style / Tone
• T — Task
• A — Audience
• R — Response format

Used together, these elements reduce trial and error and make strong results far more likely on the first attempt.

C — Context: Set the Scene

Context explains why you're asking the question and what situation the AI should assume. Without it, the AI defaults to the most general answer possible.

Think of the AI as a consultant. You wouldn't walk into a meeting and say, "Tell me about marketing." You'd explain your business, your constraints, and your goal.

Example

• Without context:

  Give me some ideas for dinner.

• With context:

  I need a 30-minute dinner using chicken, zucchini, and feta that two picky kids will eat.

The added context completely changes the quality of the response.

O — Objective: Define the Goal

The objective tells the AI exactly what success looks like. It keeps responses focused and prevents unnecessary rambling.

A clear objective answers the question: What do I want at the end?

Example

• Unclear objective:

  Tell me about the Roman Empire.

• Clear objective:

  Create a timeline of the five most important events leading to the fall of the Western Roman Empire.

S — Style and Tone: Set the Voice

AI can write in many different voices — formal, casual, humorous, or authoritative. If you don't specify tone, you'll get whatever default style the model chooses.

Defining style ensures the response fits where it will be used.

Example

• No style specified:

  Explain blockchain technology.

• Style specified:

  Explain blockchain in a friendly, enthusiastic tone, avoiding technical jargon.

T — Task: Add Rules and Constraints

The task defines how the AI should do the work. This is where you set boundaries, requirements, and non-negotiables.

Constraints help the AI stay on track.

Example

• No constraints:

  Write an email requesting vacation.

• With constraints:

  Write a professional email requesting vacation from July 15–22. Mention that major projects are complete. Do not include personal reasons.

A — Audience: Know Who It's For

Audience describes who will read the output and how much they already know. This determines complexity, language, and level of detail.

A good answer for experts may confuse beginners.

Example

• No audience specified:

  Summarize gravity.

• Audience specified:

  Explain gravity to a fifth-grade student with no science background.

R — Response: Choose the Format

Response format tells the AI how to structure the output. This step is often overlooked but saves a lot of time.

Instead of reformatting later, you get something ready to use immediately.

Example

• No format specified:

  List the pros and cons of remote work.

• Format specified:

  Format the response as a two-column markdown table with four items in each column.

Putting It All Together

Here's what a complete COSTAR prompt looks like in practice:

• Context: I write a weekly personal finance newsletter.
• Objective: Explain the 50/30/20 budgeting rule in a short, actionable article.
• Style: Friendly, encouraging, and confident, like a helpful coach.
• Task: Exactly 250 words and include one health-related metaphor.
• Audience: Young professionals (ages 22–35) who are new to budgeting.
• Response: Blog post format with a bold headline and a closing call to action.

This prompt leaves very little to chance. The AI understands the situation, goal, tone, limits, reader, and format before it starts writing.

Final Thoughts

COSTAR isn't a trick or a shortcut. It's a way of thinking.

Instead of treating AI like a search engine, you treat it like a capable assistant that needs clear direction. By consistently using Context, Objective, Style, Task, Audience, and Response, you move from casual AI use to intentional, reliable results.

Prompting well isn't about being technical.
It's about being clear.

And COSTAR gives you a simple blueprint to do exactly that.