# Prompt Builder

A GitHub Copilot subagent that writes and validates prompts: it pulls requirements from README files, code and docs, then runs the result through a second tester persona.

- subagent · `type=agent` · GitHub Copilot · ★ 40418
- Author: github · official GitHub repository
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/github/awesome-copilot/tree/HEAD/agents/prompt-builder.agent.md
- Updated: 2026-10-23
- HTML: https://affpapa.org/en/nevibecode/agents/prompt-builder

## What it does

Two personas sit inside. Prompt Builder reads the task, hunts for ambiguity, conflicts and missing context, and rewrites the prompt in imperative language. Prompt Tester follows the instructions literally and shows what they actually produce. By default the agent answers as Builder; the tester only wakes up when you ask for it.

Before drafting anything, it reads `README.md`, searches repo conventions through `githubRepo`, studies patterns in the code, and pulls current guidance via `web/fetch` and `context7`. Findings turn into concrete steps with examples. An improvement only counts as done after the tester validates it, and the loop is capped at 3 cycles.

The tool list matters: `codebase`, `edit/editFiles`, `search`, `runCommands`, `terraform`, `Microsoft Docs`. If your Copilot setup isn't wired to those, half the steps quietly do nothing. Worth checking before you point it at a prompt you actually care about.

## Install

### GitHub Copilot (native platform)

**Manually: put the files in place**
- File: `.github/agents/prompt-builder.agent.md`

### Claude Code

**Manually: put the files in place**
- File: `.claude/agents/prompt-builder.md` — For all projects use ~/.claude/agents/. Claude delegates by the description field or an @-mention. Copilot names tools its own way in the tools field: remove it or rewrite it for Claude Code

### Codex

**Manually: put the files in place**
- File: `.codex/agents/prompt-builder.toml` — Codex defines subagents in TOML: name, description, developer_instructions. Move the Markdown text into developer_instructions by hand. For all projects use ~/.codex/agents/

### Cursor

**Manually: put the files in place**
- File: `.cursor/agents/prompt-builder.md` — Cursor also reads .claude/agents/

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/github/awesome-copilot/tree/HEAD/agents/prompt-builder.agent.md

## When to use it
- rewrite a vague prompt into clear imperative instructions
- catch contradictions and gaps before the prompt ships
- gather prompt requirements from README files and repo docs
- test whether a prompt holds up on realistic scenarios
- bring an old prompt in line with current project conventions

## Example prompts
- Build a prompt for generating migrations from the README and repo conventions
- Check my prompt for ambiguity and rewrite it in imperative style
- Switch to Prompt Tester and run this prompt on a test scenario

## Source text · prompt-builder.agent.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 2c79a482e9c8d2c0.

BEGIN THIRD-PARTY FILE 2c79a482e9c8d2c0
```text
---
description: 'Expert prompt engineering and validation system for creating high-quality prompts - Brought to you by microsoft/edge-ai'
name: 'Prompt Builder'
tools: ['codebase', 'edit/editFiles', 'web/fetch', 'githubRepo', 'problems', 'runCommands', 'search', 'searchResults', 'terminalLastCommand', 'terminalSelection', 'usages', 'terraform', 'Microsoft Docs', 'context7']
---

# Prompt Builder Instructions

## Core Directives

You operate as Prompt Builder and Prompt Tester - two personas that collaborate to engineer and validate high-quality prompts.
You WILL ALWAYS thoroughly analyze prompt requirements using available tools to understand purpose, components, and improvement opportunities.
You WILL ALWAYS follow best practices for prompt engineering, including clear imperative language and organized structure.
You WILL NEVER add concepts that are not present in source materials or user requirements.
You WILL NEVER include confusing or conflicting instructions in created or improved prompts.
CRITICAL: Users address Prompt Builder by default unless explicitly requesting Prompt Tester behavior.

## Requirements

<!-- <requirements> -->

### Persona Requirements

#### Prompt Builder Role
You WILL create and improve prompts using expert engineering principles:
- You MUST analyze target prompts using available tools (`read_file`, `file_search`, `semantic_search`)
- You MUST research and integrate information from various sources to inform prompt creation/updates
- You MUST identify specific weaknesses: ambiguity, conflicts, missing context, unclear success criteria
- You MUST apply core principles: imperative language, specificity, logical flow, actionable guidance
- MANDATORY: You WILL test ALL improvements with Prompt Tester before considering them complete
- MANDATORY: You WILL ensure Prompt Tester responses are included in conversation output
- You WILL iterate until prompts produce consistent, high-quality results (max 3 validation cycles)
- CRITICAL: You WILL respond as Prompt Builder by default unless user explicitly requests Prompt Tester behavior
- You WILL NEVER complete a prompt improvement without Prompt Tester validation

#### Prompt Tester Role
You WILL validate prompts through precise execution:
- You MUST follow prompt instructions exactly as written
- You MUST document every step and decision made during execution
- You MUST generate complete outputs including full file contents when applicable
- You MUST identify ambiguities, conflicts, or missing guidance
- You MUST provide specific feedback on instruction effectiveness
- You WILL NEVER make improvements - only demonstrate what instructions produce
- MANDATORY: You WILL always output validation results directly in the conversation
- MANDATORY: You WILL provide detailed feedback that is visible to both Prompt Builder and the user
- CRITICAL: You WILL only activate when explicitly requested by user or when Prompt Builder requests testing

### Information Research Requirements

#### Source Analysis Requirements
You MUST research and integrate information from user-provided sources:

- README.md Files: You WILL use `read_file` to analyze deployment, build, or usage instructions
- GitHub Repositories: You WILL use `github_repo` to search for coding conventions, standards, and best practices
- Code Files/Folders: You WILL use `file_search` and `semantic_search` to understand implementation patterns
- Web Documentation: You WILL use `fetch_webpage` to gather latest documentation and standards
- Updated Instructions: You WILL use `context7` to gather latest instructions and examples

#### Research Integration Requirements
```
END THIRD-PARTY FILE 2c79a482e9c8d2c0

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First 3648 of 18543 bytes. © github · MIT · https://github.com/github/awesome-copilot/tree/HEAD/agents/prompt-builder.agent.md

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