prompt-builder

type	skill
lifecycle	stable
inheritance	inheritable
name	prompt-builder
description	Create and validate .prompt.md files that pass brain-qa on first attempt
tier	standard
applyTo	**/*.prompt.md,**/*prompt*
currency	2026-04-22T00:00:00.000Z

Prompt Builder

Build .prompt.md files that pass brain-qa on first attempt — no regressions

---

When to Use

• Creating a new .prompt.md file
• Fixing a failing prompt in brain-qa
• Adding prompts to the loop menu config
• Reviewing prompt frontmatter for completeness

---

Prompt Anatomy

Every .prompt.md has two parts: YAML frontmatter and Markdown body.

Frontmatter (Required Fields)

Field	Required	Gate	Purpose
description	Yes	Yes	What the prompt does (1 sentence)
application	Yes	Yes	When/why to use it (distinct from description)
mode	Conditional	No	Set to agent for loop prompts
agent	Conditional	No	Named agent for root prompts
tools	Conditional	No	Tool array for loop prompts

Gate fields (description + application) are mandatory — brain-qa fails without both.

brain-qa Scoring (4 points)

Flag	Points	Rule
desc	1	description: exists in frontmatter
app	1	application: exists in frontmatter
agent	1	agent: OR mode: agent exists
>20L	1	Body exceeds 20 lines

Pass = both gates (desc + app) AND score >= 3.

---

Two Archetypes

Root Prompts (.github/prompts/*.prompt.md)

Invoked directly by name. Typically route to a named agent.

---
description: "What this prompt does"
application: "When to use this prompt"
agent: Alex
---

Key rules:

• Use agent: to name the target agent (Alex, Researcher, Validator, etc.)
• Do NOT use mode: or tools: — those are for loop prompts
• Body should be 20+ lines with clear instructions

Loop Prompts (.github/prompts/loop/*.prompt.md)

Sidebar buttons in the extension Loop tab. Loaded by loopMenu.ts.

---
mode: agent
description: "What this prompt does"
application: "When to use this prompt"
tools: ["read_file", "create_file", "run_in_terminal"]
---

Key rules:

• Always include mode: agent
• Always include tools: array with relevant tool names
• Do NOT use agent: — loop prompts use mode-based routing
• Body should be 20+ lines with phase-based instructions

---

Field Writing Rules

description vs application

These are distinct fields — do not duplicate content between them.

Field	Answers	Example
description	"What does this do?"	"3-pass code review with confidence scoring"
application	"When should I use this?"	"Review code for correctness, security, and maintainability"

Anti-pattern: Making application a rephrasing of description.

tools Array (Loop Prompts Only)

Include only tools the prompt actually needs:

Tool	When to Include
read_file	Reads existing code or docs
create_file	Generates new files
replace_string_in_file	Edits existing files
run_in_terminal	Runs commands (build, test, deploy)
grep_search	Searches codebase for patterns
semantic_search	Semantic code search
list_dir	Explores directory structure
fetch_webpage	Web research
view_image	Image analysis
get_errors	Reads diagnostics
codebase	VS Code codebase tool
terminal	VS Code terminal tool
editFiles	VS Code edit tool

---

Body Structure

Minimum Viable Body (20+ Lines)

# {Title}

{1-2 sentence intro describing the workflow}

## Phase 1: {Discovery/Setup}

{Steps for initial context gathering}

## Phase 2: {Execution}

{Core workflow steps}

## Phase 3: {Validation}

{How to verify the work}

## Output

{What the user should expect}

Using Variables

• $ARGUMENTS — User's input text (root prompts)
• ${{input}} — VS Code variable for selected text
• Reference skills with: "Load .github/skills/{name}/SKILL.md"

---

Checklist Before Commit

Run mentally before saving any .prompt.md:

• description: present and meaningful
• application: present and distinct from description
• Root prompt has agent: OR loop prompt has mode: agent + tools:
• Body exceeds 20 lines
• No duplicate of existing prompt (check .github/prompts/)
• If loop prompt: registered in .github/config/loop-menu.json

---

Common Failures and Fixes

Failure	Cause	Fix
app=0	Missing application:	Add field after description:
desc=0	Missing description:	Add field in frontmatter
agent=0	No agent: or mode: agent	Add appropriate field
>20L=0	Body too short	Expand with phases/instructions
Score 3 but FAIL	Has score but missing a gate	Ensure both description AND application exist