Summary

Most bundled skills declare a top-level origin: key in their SKILL.md frontmatter (e.g. origin: ECC). This key isn't part of the official Agent Skills frontmatter whitelist, so skills fail validation under the official tooling.

Details

The official Agent Skills specification (https://agentskills.io/specification) allows exactly these six top-level frontmatter keys:

name, description, license, compatibility, metadata, allowed-tools

The official validator enforces this whitelist — anthropics/skills' skill-creator/scripts/quick_validate.py defines ALLOWED_PROPERTIES = {name, description, license, allowed-tools, metadata, compatibility} and rejects any other top-level key (skills-ref validate does the same).

origin is not in that set, so every skill carrying it fails official validation. In this repo that's 737 of 865 SKILL.md files (values seen: ECC, community, ECC direct-port adaptation, contributor names, etc.).

This also hurts portability: Claude.ai and the Claude API Skills upload both validate frontmatter, so these skills can't be uploaded as-is.

Suggested fix

The spec's intended home for arbitrary provenance is the metadata map (string → string). Moving the key keeps the data and passes validation:

# before
origin: ECC
# after
metadata:
 origin: ECC

This is a mechanical, scriptable change across the tree. Happy to send a PR if that'd be welcome.

Refs

• Spec: https://agentskills.io/specification
• Validator: anthropics/skills → skill-creator/scripts/quick_validate.py (ALLOWED_PROPERTIES)