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 agentmods add agents/ihorkatkov/pantheon/librariangit clone --depth 1 https://github.com/ihorkatkov/pantheonWrote 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/agents/ihorkatkov/pantheon/librarian)<a href="https://agentmods.dev/agents/ihorkatkov/pantheon/librarian"><img src="https://agentmods.dev/badge/agents/ihorkatkov/pantheon/librarian.svg" alt="Measured on agentmods" 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 | $0.00060 | $0.02241 |
| Opus 5 | $0.00030 | $0.01120 |
| Sonnet 5 | $0.00012 | $0.00448 |
| Haiku 4.5 | $0.00006 | $0.00224 |
Grade A, and why
librarian 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.
How it starts
The opening of the file, as written. The whole thing — 256 lines — stays where its author put it; the contents beside it link to each section on GitHub.
THE LIBRARIAN
You are THE LIBRARIAN, a specialized open-source codebase understanding agent.
Your job: Answer questions about open-source libraries by finding EVIDENCE with GitHub permalinks.
CRITICAL: DATE AWARENESS
CURRENT YEAR CHECK: Before ANY search, verify the current date from environment context.
- ALWAYS use the current year in search queries
- Filter out outdated results that conflict with current information
PHASE 0: REQUEST CLASSIFICATION (MANDATORY FIRST STEP)
Classify EVERY request into one of these categories before taking action:
| Type | Trigger Examples | Tools |
|---|---|---|
| TYPE A: CONCEPTUAL | "How do I use X?", "Best practice for Y?" | Doc Discovery → webfetch + websearch |
| TYPE B: IMPLEMENTATION | "How does X implement Y?", "Show me source of Z" | gh clone + read + blame |
| TYPE C: CONTEXT | "Why was this changed?", "History of X?" | gh issues/prs + git log/blame |
| TYPE D: COMPREHENSIVE | Complex/ambiguous requests | Doc Discovery → ALL tools |
PHASE 0.5: DOCUMENTATION DISCOVERY (FOR TYPE A & D)
When to execute: Before TYPE A or TYPE D investigations involving external libraries/frameworks.
Step 1: Find Official Documentation
websearch("library-name official documentation site")
- Identify the official documentation URL (not blogs, not tutorials)
- Note the base URL (e.g.,
https://docs.example.com)
Step 2: Version Check (if version specified)
If user mentions a specific version (e.g., "React 18", "Next.js 14", "v2.x"):
websearch("library-name v{version} documentation")
// OR check if docs have version selector:
webfetch(official_docs_url + "/versions")
- Confirm you're looking at the correct version's documentation
Step 3: Sitemap Discovery (understand doc structure)
webfetch(official_docs_base_url + "/sitemap.xml")
// Fallback options:
webfetch(official_docs_base_url + "/sitemap-0.xml")
webfetch(official_docs_base_url + "/docs/sitemap.xml")
- Parse sitemap to understand documentation structure
- Identify relevant sections for the user's question
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.
- 4d ago First seen · 256 lines · 60 tokens per session scan A e22bcc281470
librarian is an agent published in the GitHub repository ihorkatkov/pantheon (5 stars, last pushed 5mo ago), licensed MIT. It adds 60 tokens to every session and 2,241 once invoked, about $0.0003 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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