Ars Contexta is a Claude Code plugin that creates a personalized knowledge system from a conversation about how someone thinks and works, using connected Markdown files, note-processing skills, hooks, navigation maps, and templates. It is for people who want an owned, persistent second brain tailored to their domain. The catalogue entries are its generated skills, hooks, agent, and plugin workflow.
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 skills add agenticnotetaking/arscontexta --skill reducegit clone --depth 1 https://github.com/agenticnotetaking/arscontextaWrote 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/agenticnotetaking/arscontexta/reduce)<a href="https://agentmods.dev/skills/agenticnotetaking/arscontexta/reduce"><img src="https://agentmods.dev/badge/skills/agenticnotetaking/arscontexta/reduce/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/agenticnotetaking/arscontexta/reduce"><img src="https://agentmods.dev/badge/skills/agenticnotetaking/arscontexta/reduce.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00073 | $0.10342 |
| Opus 5.5 | $0.00029 | $0.04137 |
| Sonnet 5.5 | $0.00015 | $0.02068 |
| Haiku 4.5 | $0.00007 | $0.01034 |
Grade A, and why
reduce 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 1,120 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Runtime Configuration (Step 0 — before any processing)
Read these files to configure domain-specific behavior:
-
ops/derivation-manifest.md— vocabulary mapping, extraction categories, platform hints- Use
vocabulary.notesfor the notes folder name - Use
vocabulary.inboxfor the inbox folder name - Use
vocabulary.notefor the note type name in output - Use
vocabulary.note_pluralfor the plural form - Use
vocabulary.reducefor the process verb in output - Use
vocabulary.cmd_reflectfor the next-phase command name - Use
vocabulary.cmd_reweavefor the backward-pass command name - Use
vocabulary.cmd_verifyfor the verification command name - Use
vocabulary.extraction_categoriesfor domain-specific extraction table - Use
vocabulary.topic_mapfor MOC/topic map references - Use
vocabulary.topic_mapsfor plural form
- Use
-
ops/config.yaml— processing depth, pipeline chaining, selectivityprocessing.depth: deep | standard | quickprocessing.chaining: manual | suggested | automaticprocessing.extraction.selectivity: strict | moderate | permissive
-
ops/queue/queue.json— current task queue (for handoff mode)
If these files don't exist (pre-init invocation or standalone use), use universal defaults:
- depth: standard
- chaining: suggested
- selectivity: moderate
- notes folder:
notes/ - inbox folder:
inbox/
THE MISSION (READ THIS OR YOU WILL FAIL)
You are the extraction engine. Raw source material enters. Structured, atomic {vocabulary.note_plural} exit. Everything between is your judgment — and that judgment must err toward extraction, not rejection.
The Core Distinction
| Concept | What It Means | Example |
|---|---|---|
| Having knowledge | The vault contains information | "We store notes in folders" |
| Articulated reasoning | The vault explains WHY something works as a traversable {vocabulary.note} | "folder structure mirrors cognitive chunking because..." |
What ships with it
1 file 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.
- 1mo ago First seen · 1,120 lines · 73 tokens per session scan A caa0e753214b
reduce is a skill published in the GitHub repository agenticnotetaking/arscontexta (3,507 stars, last pushed 7mo ago), licensed MIT. It adds 73 tokens to every session and 10,342 once invoked, about $0.0003 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 2026-08-30.
Other skills, from other repositories
hyalo-okf
Maintain Open Knowledge Format vaults with Hyalo's OKF index, log, and conformance commands.
migrate
Scan the project and migrate existing documentation into OKF format. Use when the user wants to populate the knowledge base from existing docs, README, schemas, API specs, runbooks, or any structured project knowledge. Trigger on "migrate to okf", "populate the knowledge base", "scan my docs", "convert docs to okf"…
init
Initialize OKF knowledge base files in the current project. Use when the user wants to start documenting their project for claude-mega-brain, or when the user says "init mega brain", "setup the knowledge base", "cria o okf", "inicializa o mega brain", "quero usar o mega brain", "criar a estrutura do knowledge base"…
okf
Author, maintain, and consume Open Knowledge Format (OKF) knowledge bundles — portable markdown + YAML frontmatter that both humans and agents read. Use when capturing project knowledge (services, APIs, schemas, metrics, runbooks, decisions) into an OKF bundle, when updating one after code or docs change, or when a…
publishing
This skill should be used when the user asks to "self-publish", "publish my book", "ISBN", "copyright page", "book metadata", "BISAC", "keywords", "KDP", "IngramSpark", "Draft2Digital", "go wide", "Kindle Unlimited", "print interior", "trim size", "paperback", "ebook", "EPUB", "cover wrap", "spine width", "pricing"…
install-by2kb
Install, configure, update, or diagnose the by2kb CLI for this Hermes plugin. Preserve existing configuration and keep Hermes-managed plugin code separate from CLI upgrades.