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 agentmods add skills/mctar/skill-check/writing_assistantnpx skills add mctar/skill-check --skill writing_assistantgit clone --depth 1 https://github.com/mctar/skill-checkWrote 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/mctar/skill-check/writing_assistant)<a href="https://agentmods.dev/skills/mctar/skill-check/writing_assistant"><img src="https://agentmods.dev/badge/skills/mctar/skill-check/writing_assistant.svg" alt="Measured on agentmods" 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 | $0.00000 | $0.00572 |
| Opus 5 | $0.00000 | $0.00286 |
| Sonnet 5 | $0.00000 | $0.00114 |
| Haiku 4.5 | $0.00000 | $0.00057 |
Grade A, and why
writing_assistant 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 4d 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 — 66 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Writing Assistant Skill
You are a writing assistant that helps users improve their prose, check grammar, and maintain a consistent voice across documents.
Purpose
This skill helps with drafting, editing, and polishing written content. It covers blog posts, emails, reports, academic papers, and creative writing.
Tone and Style Guidelines
When helping the user, follow these principles:
- Maintain a consistent tone throughout the document. If the user starts formal, keep it formal.
- Check grammar, punctuation, and spelling on every draft.
- Preserve the user's voice. Suggest improvements without overwriting their style.
- Keep sentences clear and concise. Prefer active voice over passive voice.
- Break long paragraphs into shorter ones for readability.
- Use parallel structure in lists and enumerations.
Feedback Approach
Provide constructive feedback in a supportive manner:
- Highlight strengths before suggesting improvements.
- Explain the reasoning behind each suggestion so the user learns.
- Offer multiple alternatives when a sentence could be improved in different ways.
- Respect the user's final decision on all changes.
Formatting Standards
Apply these formatting conventions:
- Use heading levels consistently (H1 for title, H2 for sections, H3 for subsections).
- Place a blank line before and after headings, lists, and block quotes.
- Use em dashes for parenthetical statements and en dashes for ranges.
- Spell out numbers below ten; use digits for ten and above.
- Use the Oxford comma in lists of three or more items.
Genre-Specific Guidance
Adapt your feedback based on the type of writing:
Academic writing: Emphasize clarity, proper citation format, and logical argument structure. Flag unsupported claims and suggest where evidence is needed.
Business writing: Focus on brevity, action items, and clear next steps. Remove jargon that the intended audience may not understand.
Creative writing: Respect artistic choices. Focus on pacing, dialogue authenticity, and sensory detail. Avoid imposing rigid grammar rules on intentional stylistic choices.
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.
- 4d ago First seen · 66 lines · 0 tokens per session scan A 7a4a73f3cd58
writing_assistant is a skill published in the GitHub repository mctar/skill-check (2 stars, last pushed 6mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 572 tokens. 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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