Prompt Builder

Prompt Builder is an agent for Claude Code from github/awesome-copilot. It costs 24 tokens per session (3,428 once invoked), scanned A, original, MIT.

A prompt-building and testing assistant for creating, improving, and validating instructions given to AI systems. It examines requirements, structure, ambiguity, conflicts, and success criteria before producing a prompt.

In plain words
What is it for?
Use it to analyze existing prompts, find weaknesses, apply prompt-engineering practices, and create or test improved prompts.
Why use it?
It helps make AI instructions clearer, more consistent, and easier to evaluate without adding unsupported ideas.

Agent for Claude Code ✓ vendor

Written for Claude Code: a Claude Code subagent (agents/*.md).

Good fit Use it to analyze existing prompts, find weaknesses, apply prompt-engineering practices, and create or test improved prompts.

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Install with agentmods
npx agentmods add agents/github/awesome-copilot/prompt-builder
About the project

Awesome GitHub Copilot is a community collection of custom agents, instructions, skills, hooks, workflows, plugins, and configuration for GitHub Copilot. It helps Copilot users customize coding and development tasks. Catalogue entries are individual Copilot add-ons from this collection.

github/awesome-copilot · 40,192 stars · on GitHub

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/github/awesome-copilot

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for Prompt Builder

README.md
[![agentmods](https://agentmods.dev/badge/agents/github/awesome-copilot/prompt-builder/github.svg)](https://agentmods.dev/agents/github/awesome-copilot/prompt-builder)
Your own site
<a href="https://agentmods.dev/agents/github/awesome-copilot/prompt-builder"><img src="https://agentmods.dev/badge/agents/github/awesome-copilot/prompt-builder/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for Prompt Builder

Your own site · 80×15
<a href="https://agentmods.dev/agents/github/awesome-copilot/prompt-builder"><img src="https://agentmods.dev/badge/agents/github/awesome-copilot/prompt-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 24 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 3,428 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00024 $0.03428
Opus 5.5 $0.00010 $0.01371
Sonnet 5.5 $0.00005 $0.00686
Haiku 4.5 $0.00002 $0.00343

Measured 1mo ago against content hash 1f2296311ebd, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

Prompt Builder scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

5 near-identical copies found in the catalogue:

agents/prompt-builder.agent.md · 354 lines

How it starts

The opening of the file, as written. The whole thing — 354 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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

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

Read the full file on GitHub · 354 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 1mo ago First seen · 354 lines · 24 tokens per session scan A 1f2296311ebd

Subscribe to this mod's changes

Prompt Builder is an agent published in the GitHub repository github/awesome-copilot (40,192 stars, last pushed today), licensed MIT. It adds 24 tokens to every session and 3,428 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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