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 tang-vu/social-posting-skills --skill post-substackgit clone --depth 1 https://github.com/tang-vu/social-posting-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/tang-vu/social-posting-skills/post-substack)<a href="https://agentmods.dev/skills/tang-vu/social-posting-skills/post-substack"><img src="https://agentmods.dev/badge/skills/tang-vu/social-posting-skills/post-substack/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/tang-vu/social-posting-skills/post-substack"><img src="https://agentmods.dev/badge/skills/tang-vu/social-posting-skills/post-substack.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 | $0.00013 | $0.01020 |
| Opus 5 | $0.00006 | $0.00510 |
| Sonnet 5 | $0.00003 | $0.00204 |
| Haiku 4.5 | $0.00001 | $0.00102 |
Grade A, and why
post-substack 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 9d 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 — 121 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Substack Posting Skill
Platform Overview
Substack is a newsletter/blog platform where writers build direct audience relationships through email subscriptions. Ideal for long-form content, recurring updates, and building a loyal readership that you OWN (email list is exportable). 35M+ active subscriptions across all Substack publications.
Platform Constraints
- Format: Rich text editor (supports markdown import)
- Length: No limit — but 500-1,500 words is the sweet spot for newsletters
- Media: Images, embedded tweets, YouTube videos, code blocks
- SEO: Substack posts are indexed by Google and rank well
- Monetization: Built-in paid subscription support
- Email delivery: Posts are sent to all email subscribers
Posting Steps (Browser Automation)
- Navigate to
https://substack.com/publish/post - Wait for editor to load (must be logged in)
- Click on the title area and type the title/subject line
- Click below the title and type the subtitle (optional but recommended)
- Click on the body area and type the content (ASCII English only)
- Click "Publish" and choose:
- "Email + Web" (sends to subscribers AND publishes online)
- "Web only" (publishes online without emailing)
- Confirm publication
- Verify post appears on your Substack page
Content Format
# {Compelling Title -- treat like email subject line}
## {Optional Subtitle -- appears as preview text}
{Opening hook: why should the reader care? 2-3 sentences}
---
## {Section 1}
{Content with insights, examples, data}
## {Section 2}
{Content with practical advice}
## Key Takeaways
- Takeaway 1
- Takeaway 2
- Takeaway 3
---
*Subscribe for weekly updates on {topic}.*
Post Types
Newsletter (Primary)
- Sent to all email subscribers
- Shows up on your Substack page as a post
- Great for recurring content (weekly insights, roundups)
Thread (Short-form)
- Quick updates, thoughts, discussions
- Similar to social media posts
- Navigate to:
https://substack.com/publish/thread
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.
- 9d ago First seen · 121 lines · 13 tokens per session scan A d6e23e8eb237
post-substack is a skill published in the GitHub repository tang-vu/social-posting-skills (9 stars, last pushed 6mo ago), licensed MIT. It adds 13 tokens to every session and 1,020 once invoked, about $0.0001 per session on Opus 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 2026-08-31.
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