Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add markdavidgan/apple-dev-skills --skill overlay-syncgit clone --depth 1 https://github.com/markdavidgan/apple-dev-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/markdavidgan/apple-dev-skills/overlay-sync)<a href="https://agentmods.dev/skills/markdavidgan/apple-dev-skills/overlay-sync"><img src="https://agentmods.dev/badge/skills/markdavidgan/apple-dev-skills/overlay-sync/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/markdavidgan/apple-dev-skills/overlay-sync"><img src="https://agentmods.dev/badge/skills/markdavidgan/apple-dev-skills/overlay-sync.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00055 | $0.01581 |
| Opus 5.5 | $0.00022 | $0.00632 |
| Sonnet 5.5 | $0.00011 | $0.00316 |
| Haiku 4.5 | $0.00006 | $0.00158 |
Grade A, and why
overlay-sync scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 155 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Overlay Sync
Purpose: Keep thin project overlays under
.agents/skills/<prefix>-<engine>/SKILL.mdgenerated from one declarative descriptor. The provider-neutral skill is canonical; client-specific directories are compatibility surfaces owned by the project.
Why this exists
The toolkit uses a two-layer pattern: a generic engine skill in apple-dev-skills plus a small project overlay that binds it to that project's apps, schemes, paths, identity, and accepted constraints. The engine is reusable methodology; the overlay is product/repository-specific knowledge.
Do not copy generic Apple skills into an app repository. Generate only the binding layer.
Canonical project convention
For repositories that commit their own Agent Skills:
- canonical repo-owned skills:
.agents/skills/<name>/ - canonical descriptor:
apple-overlays.jsonat the repository root AGENTS.md: canonical always-on operating contract.claude/skills/: compatibility links/adapters when Claude needs themCLAUDE.md/GEMINI.md: aliases or generated wrappers around the same operating contract, never independent product truth
A legacy .claude/apple-overlays.json descriptor is accepted as a migration fallback, but new work must use root apple-overlays.json.
How it works
apple-overlays.json → node sync.mjs → .agents/skills/<prefix>-<engine>/SKILL.md
(project truth) (generator) (generated managed region)
- Author
apple-overlays.jsononce: engines plus project bindings. sync.mjslocates each engine's shippedoverlay-template.md, fills placeholders, computes app bindings, and writes the canonical project skill.- It regenerates only the managed region through
<!-- END <engine>:managed -->; hand-written project notes after that marker are preserved. - The project may then expose that canonical skill to Claude with a symlink or a tiny marked Claude-only adapter.
overlay-syncdoes not maintain vendor compatibility directories itself.
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 155 lines · 55 tokens per session scan A 94c2a40a0d8f
overlay-sync is a skill published in the GitHub repository markdavidgan/apple-dev-skills (5 stars, last pushed 1mo ago), licensed MIT. It adds 55 tokens to every session and 1,581 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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asc-metadata-sync
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