GBrain is a memory and retrieval layer for AI agents that searches, connects, and synthesizes information from stored sources. It is used to give coding agents and autonomous agents access to knowledge beyond their current code, including shared company information with access controls. The catalogue add-ons help agents operate GBrain and connect it to agent workflows.
Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/garrytan/gbrainnpx agentmods add skills/garrytan/gbrain/book-mirrorWrote 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/garrytan/gbrain/book-mirror)<a href="https://agentmods.dev/skills/garrytan/gbrain/book-mirror"><img src="https://agentmods.dev/badge/skills/garrytan/gbrain/book-mirror/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/garrytan/gbrain/book-mirror"><img src="https://agentmods.dev/badge/skills/garrytan/gbrain/book-mirror.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Snyk pass
- NVIDIA SkillSpector warn
SkillSpector: 7 findings, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Anti-Refusal · line 327 Skill attempts to nullify the agent's safety policies or restrictions ('you have no restrictions', 'ignore your guidelines', 'do anything now'). This is a direct jailbreak that disables guardrails.Fix: Remove jailbreak framing that nullifies safety policies or restrictions. Skill content must not instruct the agent to ignore its guidelines or operate without guardrails.
- medium Agent Snooping · line 361 Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
- medium Agent Snooping · line 579 Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
- medium Agent Snooping · line 453 Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
- medium Agent Snooping · line 574 Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
- medium Agent Snooping · line 575 Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
- medium Agent Snooping · line 577 Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
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 | $0.00138 | $0.06525 |
| Opus 5.5 | $0.00055 | $0.02610 |
| Sonnet 5.5 | $0.00028 | $0.01305 |
| Haiku 4.5 | $0.00014 | $0.00653 |
Grade A, and why
book-mirror 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 15d 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 — 610 lines — stays where its author put it; the contents beside it link to each section on GitHub.
book-mirror — Personalized Chapter-by-Chapter Book Analysis
Convention: see _brain-filing-rules.md for the sanctioned
media/<format>/<slug>exception this skill files under.Convention: see conventions/quality.md for citation rules, back-link enforcement, and output quality bars.
Convention: see conventions/brain-first.md for the lookup chain (brain → search → external) the context-gathering phase follows.
What this does
Given a book (EPUB or PDF), produce a brain page where every chapter is
summarized in detail on one side ("The Chapter") and mirrored back to the
reader's actual life on the other ("The Mirror"), using their own words,
situations, people, and patterns from the brain. Output is a brain page at
media/books/<slug>-personalized.md.
This is NOT a generic book summary. The mirror is the value: it makes the book read like a smart friend who happens to know the reader's life deeply is pointing things out in the margins. The mirror's job is recognition — "that's exactly me" — and then getting out of the way. If the user wants a flat summary instead, route them to a different skill.
Trust contract (read this before running)
book-mirror runs as a CLI command (gbrain book-mirror), NOT as a pure
markdown skill that the agent dispatches via tools. The CLI is the trusted
runtime; the skill is the orchestration prose around it.
What this means for the agent:
- The CLI submits N read-only subagent jobs (one per chapter). Each subagent
has
allowed_tools: ['get_page', 'search']only. They CANNOT call put_page or any mutating op. They produce markdown analysis via their final message. - The CLI reads each child's
job.result, assembles the final page, and writes it via a single operator-trustput_page. - This means untrusted EPUB/PDF content cannot prompt-inject any
people/*page. The trust narrowing happens at the tool allowlist, not at the slug-prefix layer.
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.
- 15d ago Changed 1a35187d8798
- 16d ago Changed · +1 lines 326065480665
- 18d ago Changed · +8 lines 2f69ef47fff7
- 1mo ago First seen · 601 lines · 138 tokens per session scan A 214ba954958e
book-mirror is a skill published in the GitHub repository garrytan/gbrain (31,081 stars, last pushed today), licensed MIT. It adds 138 tokens to every session and 6,525 once invoked, about $0.0006 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.
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