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.
npx agentmods add agents/dhar174/custom_github_copilot_agent_builder/prompt-buildergit clone --depth 1 https://github.com/dhar174/custom_github_copilot_agent_builderWhat 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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00021 | $0.03437 |
| Opus 5 | $0.00010 | $0.01718 |
| Sonnet 5 | $0.00004 | $0.00687 |
| Haiku 4.5 | $0.00002 | $0.00344 |
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 2d 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.
Copies of this mod
1 near-identical copy found in the catalogue:
- prompt-builder — 98% identical, 24 lines differ
How it starts
The opening of the file, as written. The whole thing — 373 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
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.
- 2d ago First seen · 373 lines · 21 tokens per session scan A 7fcbdbf8015c
prompt-builder is an agent published in the GitHub repository dhar174/custom_github_copilot_agent_builder (7 stars, last pushed 7mo ago), licensed MIT. It adds 21 tokens to every session and 3,437 once invoked, about $0.0001 per session on Opus 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 2026-08-31.
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