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 cosmicstack-labs/mercury-agent-skills --skill playlist-archivergit clone --depth 1 https://github.com/cosmicstack-labs/mercury-agent-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/cosmicstack-labs/mercury-agent-skills/playlist-archiver)<a href="https://agentmods.dev/skills/cosmicstack-labs/mercury-agent-skills/playlist-archiver"><img src="https://agentmods.dev/badge/skills/cosmicstack-labs/mercury-agent-skills/playlist-archiver/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/cosmicstack-labs/mercury-agent-skills/playlist-archiver"><img src="https://agentmods.dev/badge/skills/cosmicstack-labs/mercury-agent-skills/playlist-archiver.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 3 findings, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium Rogue Agent · line 82 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
- medium Rogue Agent · line 326 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
- medium Rogue Agent · line 373 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
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 | $0.00022 | $0.05999 |
| Opus 5 | $0.00011 | $0.03000 |
| Sonnet 5 | $0.00004 | $0.01200 |
| Haiku 4.5 | $0.00002 | $0.00600 |
Grade A, and why
playlist-archiver scanned grade A with 1 finding 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 8d 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.
Runs shell commandslowCapability
Expected in a hook, worth knowing in a rule or an instructions file.
result = subprocess.run(cmd, capture_output=True, text=True) How it starts
The opening of the file, as written. The whole thing — 798 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Playlist Archiver
Build reliable offline media archives from playlists and channels. This skill covers incremental downloading, archive management, scheduling, metadata extraction, and organizing large media collections that stay up-to-date automatically.
Core Principles
1. Archival Is Not Just Downloading
An archive is a curated, organized, and verifiable collection. You need tracking (what was downloaded when), organization (consistent folder structure), and redundancy (backups of your archive).
2. Incremental Updates Are Essential
Re-downloading everything is wasteful and risks hitting rate limits. Use archive files to track what you already have and only fetch new content. This also makes resuming interrupted operations trivial.
3. Structure Before Scale
A good directory structure scales. Design your folder hierarchy before you have 10,000 files. Flat directories are unmanageable. Use metadata variables to organize logically.
4. Plan for Long-Term Maintenance
Archives are long-term commitments. Format choices today affect accessibility tomorrow. Favor open formats (MKV, FLAC, Opus) over proprietary ones. Document your archive structure.
Playlist Downloading with yt-dlp
Basic Playlist Operations
# Download entire playlist
yt-dlp "https://youtube.com/playlist?list=PLAYLIST_ID"
# Download with organized output
yt-dlp -o "%(playlist_title)s/%(playlist_index)03d - %(title)s.%(ext)s" "URL"
# Download range of videos
yt-dlp --playlist-start 5 --playlist-end 15 "PLAYLIST_URL"
# Download newest videos first
yt-dlp --playlist-reverse "PLAYLIST_URL"
# Limit total downloads
yt-dlp --max-downloads 50 "PLAYLIST_URL"
Handling Mixed Quality
# Best quality within playlist
yt-dlp -f "bestvideo[height<=1080]+bestaudio/best[height<=1080]" \
--merge-output-format mp4 \
"PLAYLIST_URL"
# Consistent format across all videos
yt-dlp -f "bestvideo[ext=mp4][height<=720]+bestaudio[ext=m4a]/best[ext=mp4]" \
"PLAYLIST_URL"
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.
- 8d ago First seen · 798 lines · 22 tokens per session scan A 8569ff74c71d
playlist-archiver is a skill published in the GitHub repository cosmicstack-labs/mercury-agent-skills (471 stars, last pushed 17d ago), licensed MIT. It adds 22 tokens to every session and 5,999 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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