CO-STAR
The Singapore GovTech framework that won the world's first GPT-4 prompting competition.
Sheila Teo published CO-STAR in late 2023 after winning the Singapore GPT-4 Prompt Engineering World Championship organized by GovTech. The framework codifies what high-stakes business writing teams already do intuitively — separating context from objective from voice — and forces the model to honor each layer instead of collapsing them.
Every CO-STAR prompt has these sections.
Context
Background facts the model needs before reasoning — domain, constraints, prior decisions, what's already been tried.
Objective
The single, measurable outcome. Not 'help with marketing' but 'draft a 200-word LinkedIn post that drives demo signups'.
Style
The writing register — McKinsey memo, technical RFC, Hemingway-tight, conversational Slack message.
Tone
Emotional posture — confident, empathetic, urgent, neutral-analytical, playful.
Audience
Exactly who reads this — CFO, junior dev, skeptical procurement lead, 12-year-old curious about space.
Response Format
Hard schema — JSON keys, markdown headings, table columns, exact length, what to omit.
- →Customer-facing communication where tone is as important as content (sales emails, support replies, exec memos).
- →Marketing and brand voice work where audience and style must stay consistent across many outputs.
- →Anything that needs a strict response format (JSON, fixed-length, specific markdown structure).
- →Translating a vague stakeholder request into a precise model brief.
- ×Pure step-by-step procedural tasks (use RISEN — its 'Steps' slot is built for this).
- ×Long technical chains running on Claude where XML tags help (use Anthropic XML).
- ×GPT-5 production prompts that need strict role-priority hierarchy (use OpenAI Developer Message).
From one sentence to a CO-STAR section.
"Write me a follow-up to a prospect who went silent after a demo."
## Context We demoed our analytics platform 11 days ago to the Director of RevOps at a 400-person SaaS in Series C. They asked good questions, requested pricing, and have not replied to two follow-ups…
Ready to write your first CO-STAR prompt?
Drop a sentence. The Forge analyzes your task, asks the right clarifying questions, then generates a complete enterprise meta prompt structured exactly to CO-STAR.