---
type: reference
title: "Skills Architecture — Cowork 3p + CCD"
description: "Skills system schematic: Cowork Desktop 3p plugin, manifest, CCD inheritance, skill anatomy."
tags: [claude-desktop, skills, cowork, ccd, workflow]
timestamp: 2026-07-07
---

# Skills Architecture

How the skills system works between Cowork Desktop and Claude Code Desktop (CCD).

## Two skill environments

| Environment | Path | CCD Prefix | Managed by |
|----------|------|-----------------|----------------|
| **Cowork 3p** | `~/Library/Application Support/Claude-3p/local-agent-mode-sessions/skills-plugin/<uuid>/<uuid>/` | `anthropic-skills:<name>` | Cowork Desktop |
| **Claude Code global** | `~/.claude/skills/<name>/` | `<name>` (no prefix) | Manual |

**Rule:** do not duplicate skills between the two environments. Choose a single source of truth.

## Cowork 3p Plugin Structure

```
<plugin-uuid>/
└── <instance-uuid>/
    ├── .claude-plugin/
    │   └── plugin.json        → plugin namespace
    ├── manifest.json           → registry (managed by Cowork)
    └── skills/
        └── <skill-name>/
            ├── SKILL.md        → required
            ├── LICENSE.txt     → optional
            ├── scripts/        → optional (executable code)
            ├── references/     → optional (docs loaded on demand)
            ├── assets/         → optional (templates, icons, fonts)
            └── agents/         → optional (subagent instructions)
```

### manifest.json

Skills registry. Each entry:

```json
{
  "skillId": "skill-name",
  "name": "skill-name",
  "description": "When to use and what it does",
  "creatorType": "user | anthropic",
  "syncManaged": false,
  "updatedAt": "2026-07-07T20:55:26.452Z",
  "enabled": true
}
```

**Important:** Cowork Desktop manages manifest.json. Direct edits are reverted by the process. Register skills via Cowork UI or copy the folder and restart.

### How CCD discovers skills

1. CCD reads the manifest.json of the active plugin instance
2. Each skill appears as `anthropic-skills:<name>` in the available list
3. The `description` in SKILL.md frontmatter is the triggering mechanism
4. CCD does NOT read from other plugin instances

## Skill Anatomy (OKF + Bundled Resources)

Any skill (user or anthropic) can have bundled resources:

```
skill-name/
├── SKILL.md (required)
│   ├── YAML frontmatter (name, description)
│   └── Markdown instructions
└── Bundled Resources (optional)
    ├── scripts/    → executable code (PEP 723, etc.)
    ├── references/ → docs loaded into context on demand
    ├── assets/     → files used in output (templates, icons)
    └── agents/     → instructions for specialized subagents
```

### Progressive Disclosure (3 levels)

1. **Metadata** (name + description) — always in context (~100 words)
2. **SKILL.md body** — in context when skill triggers (<500 lines ideal)
3. **Bundled resources** — on demand (scripts execute without loading into context)

## skill-creator

Anthropic's official skill for creating, testing, iterating, and optimizing skills. Includes:

- Complete workflow: draft → test → eval → iterate → package
- Eval viewer for human review
- Benchmarking with variance analysis
- Description optimization to improve triggering
- Agents: grader, comparator, analyzer

Available as `anthropic-skills:skill-creator` in CCD.

## Discoveries (2026-07-07)

- Multiple plugin instances exist under `skills-plugin/` (different UUIDs)
- CCD only reads from the active instance
- Copying skill folder between instances + restarting Cowork is sufficient to register
- `/reload-skills` in CCD reloads the available skills list
- `creatorType` and bundled resources are metadata, not limitations — user skills can have everything