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Run npx skillmds@latest add mizchi/check-similarity in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

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Who published Check Similarity?

mizchi (@mizchi) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Check Similarity by mizchi — Agent Skill

Name: Check Similarity
Author: mizchi

Check Similarity

Detect duplicate code using AST-based similarity analysis. Auto-selects the right tool based on file types in the project (similarity-ts for TypeScript/JavaScript, similarity-py for Python, similarity-mbt for MoonBit, similarity-rs for Rust, etc).

mizchi Updated Sep 17, 2026

File contents

Code Similarity Detection (Multi-Language)

What to do

Detect which languages are present in the target path and run the appropriate similarity tool. Then analyze results and propose refactoring.

Step 1: Detect language and select tool

Check the target path for file extensions:

Extension	Tool
`.ts`, `.tsx`, `.js`, `.jsx`	`similarity-ts`
`.py`	`similarity-py`
`.mbt`	`similarity-mbt`
`.rs`	`similarity-rs`
`.php`	`similarity-php`
`.ex`, `.exs`	`similarity-elixir`
`.css`, `.scss`	`similarity-css`

Before running, check if the command exists. If not, install it:

which similarity-<lang> || cargo install similarity-<lang>

Step 2: Run analysis

similarity-<lang> $ARGUMENTS

If no arguments given:

similarity-<lang> . --threshold 0.85 --min-lines 5

For TypeScript, also consider type similarity:

similarity-ts . --threshold 0.85 --min-tokens 25 --experimental-types

Step 3: Analyze and report

Categorize results by priority:

100% similarity: Exact duplicates - must refactor
95-100%: Near-identical - high-value refactoring targets
85-95%: Same pattern - consider extracting shared logic
< 85%: Similar structure - investigate if related

Report the findings grouped by file, sorted by similarity (highest first). For each high-priority pair, propose a concrete refactoring with before/after code.

Common Options (all tools)

Option	Description
`--threshold <0-1>`	Similarity threshold (default: 0.85)
`--min-lines <n>`	Skip short functions (default: 3)
`--print`	Show code snippets
`--fail-on-duplicates`	Exit code 1 if duplicates found
`--filter-function <name>`	Filter by function name

CI Integration

# Fail CI if near-exact duplicates exist
similarity-<lang> . --threshold 0.95 --min-lines 5 --fail-on-duplicates

---name: check-similaritydescription: Detect duplicate code using AST-based similarity analysis. Auto-selects the right tool based on file types in the project (similarity-ts for TypeScript/JavaScript, similarity-py for Python, similarity-mbt for MoonBit, similarity-rs for Rust, etc).---# Code Similarity Detection (Multi-Language)## What to doDetect which languages are present in the target path and run the appropriate similarity tool. Then analyze results and propose refactoring.## Step 1: Detect language and select toolCheck the target path for file extensions:| Extension | Tool ||-----------|------|| `.ts`, `.tsx`, `.js`, `.jsx` | `similarity-ts` || `.py` | `similarity-py` || `.mbt` | `similarity-mbt` || `.rs` | `similarity-rs` || `.php` | `similarity-php` || `.ex`, `.exs` | `similarity-elixir` || `.css`, `.scss` | `similarity-css` |Before running, check if the command exists. If not, install it:```bashwhich similarity-<lang> || cargo install similarity-<lang>```## Step 2: Run analysis```bashsimilarity-<lang> $ARGUMENTS```If no arguments given:```bashsimilarity-<lang> . --threshold 0.85 --min-lines 5```For TypeScript, also consider type similarity:```bashsimilarity-ts . --threshold 0.85 --min-tokens 25 --experimental-types```## Step 3: Analyze and reportCategorize results by priority:1. **100% similarity**: Exact duplicates - must refactor2. **95-100%**: Near-identical - high-value refactoring targets3. **85-95%**: Same pattern - consider extracting shared logic4. **< 85%**: Similar structure - investigate if relatedReport the findings grouped by file, sorted by similarity (highest first).For each high-priority pair, propose a concrete refactoring with before/after code.## Common Options (all tools)| Option | Description ||--------|-------------|| `--threshold <0-1>` | Similarity threshold (default: 0.85) || `--min-lines <n>` | Skip short functions (default: 3) || `--print` | Show code snippets || `--fail-on-duplicates` | Exit code 1 if duplicates found || `--filter-function <name>` | Filter by function name |## CI Integration```bash# Fail CI if near-exact duplicates existsimilarity-<lang> . --threshold 0.95 --min-lines 5 --fail-on-duplicates```

Frequently asked questions