Metric Pack Designer Skill

Metric Pack Designer

Use this skill when the user wants to extend cc-plugin-eval with a local rubric.

Invoke the shipped script through the plugin root, which works in any checkout: node "${CLAUDE_PLUGIN_ROOT}/scripts/cc-plugin-eval.js" <command> <args>. Inline mentions of cc-plugin-eval <command> are shorthand for that same invocation; the bare cc-plugin-eval alias only exists if you ran npm link in the plugin directory.

Workflow

Clarify the custom rubric categories and target kinds (skill, plugin, directory).
Define the smallest useful checks[] and metrics[] payload that answers the user's actual question.
Create a metric-pack manifest plus a script that prints JSON to stdout.
Wire the pack into a run with cc-plugin-eval analyze <path> --metric-pack <manifest.json>. Repeat the flag for multiple packs.

Manifest Shape

{
  "name": "team-rubric",
  "version": "1.0.0",
  "supportedTargetKinds": ["skill", "plugin"],
  "command": ["node", "./emit-team-rubric.js"]
}

Runtime Contract

The manifest is passed to cc-plugin-eval analyze --metric-pack <manifest.json>.
The command runs from the manifest directory.
The target path and target kind are appended as CLI arguments.
The process also receives:
- CC_PLUGIN_EVAL_TARGET
- CC_PLUGIN_EVAL_TARGET_KIND
- CC_PLUGIN_EVAL_METRIC_PACK_MANIFEST

Output Contract

The metric pack must print JSON to stdout in this shape:

{
  "checks": [
    {
      "id": "team-style",
      "category": "custom",
      "severity": "warning",
      "status": "warn",
      "message": "Custom rubric finding",
      "evidence": ["detail"],
      "remediation": ["fix detail"]
    }
  ],
  "metrics": [
    {
      "id": "team-score",
      "category": "custom",
      "value": 4,
      "unit": "points",
      "band": "good"
    }
  ],
  "artifacts": []
}

Design Rules

Keep IDs stable across runs so cc-plugin-eval compare stays meaningful.
Emit only checks[], metrics[], and optional artifacts[].
Do not try to overwrite the core summary or the budget bucket totals.
Prefer deterministic local signals over subjective text generation.
Use unique IDs that do not collide with the built-in CC1xx-CC9xx codes.

Reference

../../references/metric-pack-manifest.md
../../references/evaluation-result-schema.md

Agent Skills: Metric Pack Designer

Install this agent skill to your local