Borrowing it
Nothing to install: this file belongs to swaaap-nil/system-design-skill. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/swaaap-nil/system-design-skill/main/AGENTS.mdgit clone --depth 1 https://github.com/swaaap-nil/system-design-skillWrote 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.
[](https://agentmods.dev/instructions/swaaap-nil/system-design-skill/agents-md)<a href="https://agentmods.dev/instructions/swaaap-nil/system-design-skill/agents-md"><img src="https://agentmods.dev/badge/instructions/swaaap-nil/system-design-skill/agents-md/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.
<a href="https://agentmods.dev/instructions/swaaap-nil/system-design-skill/agents-md"><img src="https://agentmods.dev/badge/instructions/swaaap-nil/system-design-skill/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00380 | $0.00380 |
| Opus 5.5 | $0.00152 | $0.00152 |
| Sonnet 5.5 | $0.00076 | $0.00076 |
| Haiku 4.5 | $0.00038 | $0.00038 |
Grade A, and why
system-design-skill AGENTS.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 2mo 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.
What it actually says
AGENTS.md
Instructions for AI coding agents working in this repository.
What this repo is
A single Agent Skill — skills/system-design-interview/ — plus the
installers that place it into other repositories. There is no application code.
skills/system-design-interview/ is the single source of truth. The installers copy it; they
never generate it. Installed copies under .agents/, .claude/, .codex/ and friends are
gitignored, so never edit those — the change will be silently discarded on the next install.
Working here
- Editing the skill's behaviour →
skills/system-design-interview/SKILL.md. Keep it under 500 lines; detail belongs inreferences/. - Adding a scaling anti-pattern →
references/bottlenecks.md, matching the existing detect / breaks-at / fix / trade-off / verify structure. - Adding stack coverage →
references/recon.md, one table row per stack. - Changing install behaviour →
bin/install.mjs(Node) andinstall.sh(POSIX sh). The two must stay in agreement about which directories they write.
Before committing
node scripts/check-skill.mjs # Agent Skills spec compliance
sh -n install.sh # shell installer syntax
./install.sh --all --dir "$(mktemp -d)"
Using the skill itself
To run the skill on this repository or any other, install it first:
./install.sh
Then invoke /system-design-interview. Note that this repo is a poor target for it — it has no
server, no data model and no hot path, and the skill is instructed to say so rather than invent one.
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.
- 2mo ago First seen · 42 lines · 380 tokens per session scan A 85b6c253a3a7
system-design-skill AGENTS.md is an instructions file published in the GitHub repository swaaap-nil/system-design-skill (2 stars, last pushed 2mo ago), licensed MIT. It adds 380 tokens to every session, about $0.0015 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 2026-08-31.
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