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-new-sensorgit 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-new-sensor)<a href="https://agentmods.dev/skills/tacoda/keystone/keystone-new-sensor"><img src="https://agentmods.dev/badge/skills/tacoda/keystone/keystone-new-sensor.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 | $0.00015 | $0.00424 |
| Opus 5 | $0.00008 | $0.00212 |
| Sonnet 5 | $0.00003 | $0.00085 |
| Haiku 4.5 | $0.00002 | $0.00042 |
Grade A, and why
keystone-new-sensor 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 7d 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:new-sensor — scaffold a sensor
A sensor is an automated check the charter fires inside an action. Two kinds exist:
- computational — deterministic execution (binary, script, library). Examples: unit-test runner, type checker, linter, build command.
- inferential — produced by agent reasoning. Examples: functional review, security review, spec-acceptance walk.
Sensors live at .charter/sensors/<name>.md and declare
kind: (computational or inferential) in frontmatter.
Run
keystone new sensor <name> [--kind <kind>]
Examples:
keystone new sensor lint # default kind: computational
keystone new sensor security --kind inferential # explicit inferential
After scaffolding
- Fill in
## Command— for computational sensors, the exact shell invocation. For inferential, the prompt the agent runs. - Fill in
## Interpretation— what pass / fail look like. - Fill in
## Remediation— what the agent does on failure. - Wire the sensor into the relevant action (
verify,check-drift, etc.) via itsdeps:frontmatter or its## Activitieslist. - Run
keystone indexto refresh the descriptor surface.
Full port contract:
docs/ports/sensor.md.
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.
- 7d ago First seen · 62 lines · 15 tokens per session scan A bb95615044c0
keystone-new-sensor is a skill published in the GitHub repository tacoda/keystone (44 stars, last pushed 2mo ago), licensed MIT. It adds 15 tokens to every session and 424 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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