second-brain-query

second-brain-query is a skill for Claude Code, Codex from philipyaz/cos. It costs 134 tokens per session (1,416 once invoked), scanned A, original, MIT.

A read-only question-answering tool for a knowledge wiki split into work and life areas, using linked wiki pages as citations.

In plain words
What is it for?
Use it to answer questions about work, personal matters, or both by searching the relevant wiki and following its internal links. It does not edit the wiki or access a task board.
Why use it?
It answers from stored notes rather than the currently open work, while showing which linked pages support the answer and pointing to related files.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/philipyaz/cos/second-brain-query
Any agent
npx skills add philipyaz/cos --skill second-brain-query
Clone the repo
git clone --depth 1 https://github.com/philipyaz/cos

Made for: Claude Code, Codex.

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 second-brain-query

README.md
[![agentmods](https://agentmods.dev/badge/skills/philipyaz/cos/second-brain-query.svg)](https://agentmods.dev/skills/philipyaz/cos/second-brain-query)
Your own site
<a href="https://agentmods.dev/skills/philipyaz/cos/second-brain-query"><img src="https://agentmods.dev/badge/skills/philipyaz/cos/second-brain-query.svg" alt="Measured on agentmods" height="20"></a>
Per session 134 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,416 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00134 $0.01416
Opus 5 $0.00067 $0.00708
Sonnet 5 $0.00027 $0.00283
Haiku 4.5 $0.00013 $0.00142

Measured 4d ago against content hash eeb1091e81af, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

second-brain-query 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 4d 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.

vault/example-vault/.claude/skills/second-brain-query/SKILL.md · 108 lines

How it starts

The opening of the file, as written. The whole thing — 108 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Second Brain — Query (knowledge-only, read-only)

Answer questions by searching and synthesizing knowledge from the domain-split wiki. This skill is read-only — it never writes, edits, or runs commands. It also has no board access: it answers from knowledge, not from open work.

CORE LOOP

1. Determine the domain — work | life | both

From the question, decide which wiki tree(s) to search:

  • work — the venture, the role, advisory, work contacts/projects → work/wiki.
  • life — trips, health, admin, family, personal logistics → life/wiki.
  • both — a question that spans the two (the user themself, the home city, anything touching shared/wiki entities, or an explicitly cross-cutting question) → search work/wiki and life/wiki, plus shared/wiki.

When unsure, prefer both and let the index tell you which side actually has the answer.

2. Enter through the strong index

Read <domain>/wiki/index.md — the strong index is the entry point. It is a map of overarching themes, each grouping its concepts, entities, and sources. Find the theme(s) relevant to the question and the specific [[pages]] listed under them. The index, not a directory scan, is how you locate the right pages fast.

3. Follow the [[wikilinks]]

Read the pages the index points you to, then follow their [[wikilinks]] to pull in related context (linked entities, concepts, and source pages). Read enough to answer thoroughly — but don't read the whole wiki. If the wiki pages don't fully answer, drop to the relevant <domain>/wiki/sources/ pages for detail; go to raw/ only as a last resort.

4. Surface associated artifacts (CRUCIAL)

For the pages you cite, also surface any associated artifacts — files under raw/assets/ linked from those pages (the source pages reference preserved attachments via relative markdown links like ../../raw/assets/<file>). List their paths in your answer so the user can retrieve the original artifact, not just the synthesized text. If a cited page links an asset, name it.

Read the full file on GitHub · 108 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. 4d ago First seen · 108 lines · 134 tokens per session scan A eeb1091e81af

Subscribe to this mod's changes

second-brain-query is a skill published in the GitHub repository philipyaz/cos (4 stars, last pushed today), licensed MIT. It adds 134 tokens to every session and 1,416 once invoked, about $0.0007 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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