# Scan Disk

> Minimal example Observe-phase domain skill. Checks disk usage and records it. Copy this as a starting point for your own domain.

- Skill: `mataeil/scan-disk` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add mataeil/scan-disk`
- Raw SKILL.md: https://api.skillmd.com/api/skills/mataeil/scan-disk/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: mataeil (https://skillmd.com/u/mataeil)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/mataeil/scan-disk

---


# /scan-disk — Minimal Domain Skill Example

The smallest useful Observe skill: it reads disk usage, records a baseline, and
emits an alert when usage crosses a learned threshold. Use it as a 30-line
template for your own domain. **Every skill starts with a HALT check.**

## Step 0: Safety

```bash
ls agent/safety/HALT 2>/dev/null && echo "HALT_ACTIVE" || echo "HALT_INACTIVE"
```

If HALT is active, print the reason and stop immediately.

## Step 1: Observe

```bash
df -P / | tail -1 | awk '{print $5}' | tr -d '%'   # → integer percent used
```

Load the lens (`agent/state/disk_usage/lens.json`) if present. Use its
`learned_thresholds` for `warn_pct` if it has one; otherwise default `warn_pct = 85`.

## Step 2: Record + alert

Write `agent/state/disk_usage/state.json`:

```json
{
  "schema_version": "1.0.0",
  "last_run": "<now ISO-8601>",
  "status": "healthy",            // healthy | degraded | critical
  "metrics": { "used_pct": 73 },
  "alerts": []                    // e.g. ["disk 91% > warn_pct 85"] when crossed
}
```

Set `status: "degraded"` and add an alert when `used_pct >= warn_pct`;
`"critical"` at `>= 95`. The evolve engine reads `status`/`alerts` during Observe
and factors them into scoring.

## Adaptive Lens (optional but recommended)

evolve's Step 5-E initializes and updates `agent/state/disk_usage/lens.json`
automatically. To participate, just emit consistent `metrics`/`alerts`; the engine
learns a per-host `warn_pct` over time (raising it on repeated false positives,
lowering it after real incidents). You don't write the lens yourself.