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 tacoda/keystone --skill keystone-indexgit clone --depth 1 https://github.com/tacoda/keystoneWrote 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/tacoda/keystone/keystone-index)<a href="https://agentmods.dev/skills/tacoda/keystone/keystone-index"><img src="https://agentmods.dev/badge/skills/tacoda/keystone/keystone-index.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 5.1 | $0.00020 | $0.00349 |
| Opus 5 | $0.00010 | $0.00175 |
| Sonnet 5 | $0.00004 | $0.00070 |
| Haiku 4.5 | $0.00002 | $0.00035 |
Grade A, and why
keystone-index 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 8d 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.
What it actually says
keystone:index — refresh the primitive descriptor index
The agent's session-start path is "read .keystone/INDEX.json, then
open primitive bodies on demand." When canonical charter files change,
the index goes stale and the agent's view of what is available diverges
from what is on disk.
This skill regenerates the index by invoking the keystone CLI.
Run
From the project root:
keystone index
The command writes .keystone/INDEX.json and prints the primitive
count. Idempotent — safe to run repeatedly.
When to trigger
- After authoring or editing any file under
.charter/. - After running
keystone migrate(the migrator regenerates the index automatically, but a re-run is cheap if drift is suspected). - Before reading
.keystone/INDEX.jsonlater in the same session if any primitive file has changed since session start.
Failure modes
- "keystone: command not found" — the binary is not on PATH. Confirm
with
which keystone. - "parse frontmatter: ..." on stderr — a primitive file has malformed YAML frontmatter; the indexer reports the path. Fix the file and re-run.
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.
- 8d ago First seen · 52 lines · 20 tokens per session scan A a16d01117c0f
keystone-index is a skill published in the GitHub repository tacoda/keystone (44 stars, last pushed 2mo ago), licensed MIT. It adds 20 tokens to every session and 349 once invoked, about $0.0001 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 2026-08-30.
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