grammar-check

grammar-check is a skill for Claude Code, Codex from yuusakuri/agent-skills. It costs 37 tokens per session (2,148 once invoked), scanned A, a copy of grammar-check, MIT.

A writing review skill that finds grammar, reasoning, and flow problems in text and suggests focused fixes.

In plain words
What is it for?
Use it to proofread emails, marketing copy, technical documents, presentations, or other drafts and get specific correction suggestions.
Why use it?
It helps improve a draft without replacing the writer’s whole document, while keeping the intended audience and purpose in view.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to proofread emails, marketing copy, technical documents, presentations, or other drafts and get specific correction suggestions.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/yuusakuri/agent-skills/grammar-check
Install

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.

Any agent
npx skills add yuusakuri/agent-skills --skill grammar-check
Clone the repo
git clone --depth 1 https://github.com/yuusakuri/agent-skills

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for grammar-check

README.md
[![agentmods](https://agentmods.dev/badge/skills/yuusakuri/agent-skills/grammar-check/github.svg)](https://agentmods.dev/skills/yuusakuri/agent-skills/grammar-check)
Your own site
<a href="https://agentmods.dev/skills/yuusakuri/agent-skills/grammar-check"><img src="https://agentmods.dev/badge/skills/yuusakuri/agent-skills/grammar-check/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.

agentmods 80×15 button for grammar-check

Your own site · 80×15
<a href="https://agentmods.dev/skills/yuusakuri/agent-skills/grammar-check"><img src="https://agentmods.dev/badge/skills/yuusakuri/agent-skills/grammar-check.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 37 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,148 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00037 $0.02148
Opus 5 $0.00018 $0.01074
Sonnet 5 $0.00007 $0.00430
Haiku 4.5 $0.00004 $0.00215

Measured 12d ago against content hash 67e4721b2554, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

grammar-check 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 12d 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.

Origin

This is a copy

100% identical to grammar-check — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/grammar-check/SKILL.md · 210 lines

How it starts

The opening of the file, as written. The whole thing — 210 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Grammar and Flow Checking

You are an expert copyeditor and writing specialist. Your role is to identify grammar, logical, and flow errors in text, then provide clear, actionable fix suggestions without rewriting the entire document.

Purpose

Analyze text for grammar, logical, and flow errors. Provide specific, focused suggestions on how to fix each issue. Focus on clarity, correctness, and readability.

Input Arguments

  • $OBJECTIVE: What is the intended purpose or goal of the text? (e.g., "persuade investors to fund our Series A," "explain product features to new users," "communicate company values to employees")
  • $TEXT: The text to review

Process

Step 1: Understand Context

  • Note the objective: Is this marketing copy, technical documentation, a presentation, an email, social media content?
  • Identify the target audience: Experts, general public, stakeholders, customers?
  • Consider tone: Formal, casual, authoritative, friendly?

Step 2: Scan for Errors

Read through the text once, identifying:

  • Grammar errors: Spelling, punctuation, subject-verb agreement, tense consistency, modifier placement
  • Logical errors: Contradictions, unsupported claims, unclear cause-and-effect, incomplete thoughts
  • Flow errors: Choppy transitions, unclear organization, redundancy, passive voice overuse, vague pronouns, awkward phrasing

Step 3: Categorize Errors

Organize findings by type:

  1. Grammar (spelling, punctuation, syntax)
  2. Logic (clarity, coherence, reasoning)
  3. Flow (transitions, sentence structure, readability, tone consistency)

Step 4: Create Fix Suggestions

For each error, provide:

  • Location: Where in the text (e.g., "Paragraph 3, sentence 2")
  • Error identified: What's wrong
  • Fix suggested: How to correct it
  • Rationale: Why this matters (clarity, grammar rule, flow, tone)

Step 5: Prioritize

Flag highest-impact issues first:

  • Critical: Grammar or logic errors that confuse readers
  • Important: Flow issues that hurt readability or persuasiveness
  • Minor: Stylistic suggestions or polish

Read the full file on GitHub · 210 lines

Changes

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.

  1. 12d ago First seen · 210 lines · 37 tokens per session scan A 67e4721b2554

Subscribe to this mod's changes

grammar-check is a skill published in the GitHub repository yuusakuri/agent-skills (2 stars, last pushed 6d ago), licensed MIT. It adds 37 tokens to every session and 2,148 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to grammar-check, differing in 0 lines, and is treated as a copy.

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