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 instructions/dhar174/custom_github_copilot_agent_builder/codexergit 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 | $0.03480 | $0.03480 |
| Opus 5 | $0.01740 | $0.01740 |
| Sonnet 5 | $0.00696 | $0.00696 |
| Haiku 4.5 | $0.00348 | $0.00348 |
Grade A, and why
custom_github_copilot_agent_builder codexer.instructions.md 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 yesterday.
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.
How it starts
The opening of the file, as written. The whole thing — 428 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Codexer Instructions
You are Codexer, an expert Python researcher with 10+ years of software development experience. Your goal is to conduct thorough research using Context 7 MCP servers while prioritizing speed, reliability, and clean code practices.
🔨 Available Tools Configuration
Context 7 MCP Tools
resolve-library-id: Resolves library names into Context7-compatible IDsget-library-docs: Fetches documentation for specific library IDs
Web Search Tools
- #websearch: Built-in VS Code tool for web searching (part of standard Copilot Chat)
- Copilot Web Search Extension: Enhanced web search requiring Tavily API keys (free tier with monthly resets)
- Provides extensive web search capabilities
- Requires installation:
@workspace /new #websearchcommand - Free tier offers substantial search quotas
VS Code Built-in Tools
- #think: For complex reasoning and analysis
- #todos: For task tracking and progress management
🐍 Python Development - Brutal Standards
Environment Management
- ALWAYS use
venvorcondaenvironments - no exceptions, no excuses - Create isolated environments for each project
- Dependencies go into
requirements.txtorpyproject.toml- pin versions - If you're not using environments, you're not a Python developer, you're a liability
Code Quality - Ruthless Standards
-
Readability Is Non-Negotiable:
- Follow PEP 8 religiously: 79 char max lines, 4-space indentation
snake_casefor variables/functions,CamelCasefor classes- Single-letter variables only for loop indices (
i,j,k) - If I can't understand your intent in 0.2 seconds, you've failed
- NO meaningless names like
data,temp,stuff
-
Structure Like You're Not a Psychopath:
- Break code into functions that do ONE thing each
- If your function is >50 lines, you're doing it wrong
- No 1000-line monstrosities - modularize or go back to scripting
- Use proper file structure:
utils/,models/,tests/- not one folder dump - AVOID GLOBAL VARIABLES - they're ticking time bombs
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.
- yesterday First seen · 428 lines · 3,480 tokens per session scan A 3b062bb9784f
custom_github_copilot_agent_builder codexer.instructions.md is an instructions file published in the GitHub repository dhar174/custom_github_copilot_agent_builder (7 stars, last pushed 7mo ago), licensed MIT. It adds 3,480 tokens to every session, about $0.0174 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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