Borrowing it
Nothing to install: this file belongs to the-sid-dani/second-brain-os. 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/the-sid-dani/second-brain-os/main/.agents/skills/os-guide/SKILL.mdgit clone --depth 1 https://github.com/the-sid-dani/second-brain-osWrote 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/skills/the-sid-dani/second-brain-os/os-guide)<a href="https://agentmods.dev/skills/the-sid-dani/second-brain-os/os-guide"><img src="https://agentmods.dev/badge/skills/the-sid-dani/second-brain-os/os-guide/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/skills/the-sid-dani/second-brain-os/os-guide"><img src="https://agentmods.dev/badge/skills/the-sid-dani/second-brain-os/os-guide.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 | $0.00102 | $0.06800 |
| Opus 5.5 | $0.00041 | $0.02720 |
| Sonnet 5.5 | $0.00020 | $0.01360 |
| Haiku 4.5 | $0.00010 | $0.00680 |
Grade B, and why
os-guide scanned grade B with 1 finding 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 7d 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.
Enumerates other installed skillsmediumAgent snooping
Other skills' SKILL.md files reveal prompts, capabilities and secrets that should be invisible to peers.
| All available skills | `find -L .claude/skills -mindepth 2 -maxdepth 2 -name SKILL.md` then read each frontmatter `description:` line | Follow symlinks, validate frontmatter, and never hardcode the list | How it starts
The opening of the file, as written. The whole thing — 437 lines — stays where its author put it; the contents beside it link to each section on GitHub.
os-guide
Runtime-read librarian over the second-brain OS's canonical source files. Answers "how does X work in this OS?" without ever embedding facts that could drift. Every response carries file:line citations.
Before you begin: read the Configuration section in root CLAUDE.md (locate via grep -n "^## Configuration" — it moves as sections are added). Path tokens like <workspace.root>, <workspace.projects>, <assistant.name> resolve from there — don't hardcode them in answers.
⚠️ Meta-instruction (for Claude reading this skill)
If you are about to give an OS-shaped answer from memory rather than reading the canonical source — STOP and invoke this skill instead. That includes any answer that contains:
- A workspace path (e.g.,
<workspace.root>/...) - A Configuration token value (
workspace.projects,user.email,assistant.name, etc.) - A claim about a skill's behavior or scope
- A claim that a tool is or isn't installed
- A schema field (contacts, design systems, project frontmatter)
- A locked design decision (if your fork maintains a design-log file)
Memory drifts. Canonical files don't. This skill exists to make the latter cheap to consult.
Why this exists
The OS has seven+ canonical sources (CLAUDE.md, README.md, SOUL.md, USER.md, IDENTITY.md, TOOLS.md, contacts/README.md, plus individual SKILL.md files — and your own design log if you keep one). Without /os-guide, answering "where does X live?" or "what's the rule about Y?" is a manual ritual of grep + cat + remembering which file owns which topic.
The naive alternative — encoding the answers in a tutorial-style skill body — fails the moment any canonical source drifts. The core principle this skill enforces: explainer skills MUST be runtime-read librarians, not textbooks. Reference, don't reproduce (per SOUL.md Operating Principles).
Two audiences:
- Claude Code, self-correcting mid-session (primary) — about to write a path, a config value, or a skill claim; pauses to verify.
- Fork users in their first 30 days (secondary) — figuring out PARA, the Configuration pattern, how to connect a tool, what skills exist.
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 7d ago Changed · +12 lines · -81 tokens per session a35790ab8f3b
- 1mo ago First seen · 425 lines · 183 tokens per session scan B c40ab45c9812
os-guide is a skill published in the GitHub repository the-sid-dani/second-brain-os (3 stars, last pushed 7d ago), licensed MIT. It adds 102 tokens to every session and 6,800 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it B with 1 finding (enumerates other installed skills). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
Other skills, from other repositories
screenpipe-api
Query the user's local and synced-device data via the screenpipe REST API at localhost:3030 — recordings, audio, UI, meetings, connected services, and memory. Use for screen activity, other-device or cross-device history, productivity, media export, connections, durable memory, or discovering and automating saved…
follower-onboard
Onboard a new machine as a receive-only follower on a multi-machine agent network: it reads the shared vault, canon, skills and memory, runs nothing heavy locally (no RAG, reindex or GPU), and never receives executable hooks from the hub. Checklist-driven, with a verify step at each stage. Triggers: "/follower-onboard…
brain-onboard
An onboarding workflow that helps another person create and use their own private knowledge store, sometimes called a second brain. It gathers their information with consent, saves it in their own workspace, and demonstrates a first useful result.
memory-tidy
Tidy an agent's always-loaded memory index (MEMORY.md) on macOS or Linux: trim long lines, move closed entries to an archive, fold domains into hub files, restore dropped pins and add pointers for orphan memory files. Use when the index is over budget or has orphans. Triggers: /memory-tidy, /mt, tidy memory.
claudeai-sync
Pull new and changed claude.ai web conversations into an Obsidian vault, extract artifacts as first-class notes, concept-link them, and refresh the RAG index and dashboard. Idempotent: curated notes are never overwritten. Triggers: "/claudeai-sync", "pull claude.ai", "grab new claude.ai chats".
chat-search
Search inside past agent sessions and continue the one that matters with a single command. Uses a separate episodic session index, so raw chat noise never pollutes the curated RAG. Triggers: "/chat-search", "which chat discussed X", "did we already research X", "search old chats".