metric-pack-designer

name	metric-pack-designer
description	Build a local rubric extension so a team can add custom checks that emit schema-compatible findings, metrics, and artifacts on top of the deterministic engine. Use when the user wants their own scoring rules, domain-specific audits, or a custom report wired into analyze runs.

Metric Pack Designer

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

Workflow

1. Clarify the custom rubric categories and target kinds (skill, plugin, directory).
2. Define the smallest useful checks[] and metrics[] payload that answers the user's actual question.
3. Create a metric-pack manifest plus a script that prints JSON to stdout.
4. 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