add-skill

A command that adds a new skill—a reusable set of instructions—to a Claude Code plugin.

In plain words
What is it for?
Use it to add a named skill with an optional description from either a plugin directory or a marketplace directory.
Why use it?
It creates the expected skill folder and SKILL.md file, so you do not have to assemble the structure by hand.

Command

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.

agentmods
npx agentmods add commands/kossakovsky/cc-plugins/add-skill
Clone the repo
git clone --depth 1 https://github.com/kossakovsky/cc-plugins
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,945 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 97% 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 $0.00000 $0.02945
Opus 5 $0.00000 $0.01473
Sonnet 5 $0.00000 $0.00589
Haiku 4.5 $0.00000 $0.00295

Measured 2d ago against content hash 625d19b59616, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

add-skill 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 2d 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

97% identical to add-skill — 6 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.

plugins/plugin-development/commands/add-skill.md · 392 lines

How it starts

The opening of the file, as written. The whole thing — 392 lines — stays where its author put it; the contents beside it link to each section on GitHub.


description: Add a new Skill to the current plugin with proper structure argument-hint: [skill-name] ["description"]

Add Skill

Create a new Skill folder with SKILL.md and supporting directories.

Arguments

  • $1 (required): Skill name in kebab-case (e.g., code-review)
  • $2 (optional): Description of when to use this Skill in quotes (e.g., "Use when reviewing code or PRs")
  • --plugin=<plugin-name> (optional): Specify which plugin to add the skill to

Usage:

# From within a plugin directory, with description
/plugin-development:add-skill code-review "Use when reviewing code or analyzing pull requests"

# Without description (uses default)
/plugin-development:add-skill code-review

# From marketplace root, specifying plugin
/plugin-development:add-skill code-review "Use when reviewing code" --plugin=plugin-development

Prerequisites

  • Must be run from either:
    • A plugin root directory (containing .claude-plugin/plugin.json), OR
    • A marketplace root directory (containing .claude-plugin/marketplace.json)
  • skills/ directory will be created if needed

Instructions

Validation

IMPORTANT: When running test commands for validation (checking directories, files, etc.), use require_user_approval: false since these are read-only checks.

  1. Detect context and target plugin (output thoughts during this process):

    a. Check if we're in a plugin directory:

    • Look for .claude-plugin/plugin.json in current directory
    • Output: "Checking for plugin directory..."
    • If found:
      • Output: "Found plugin.json - using current directory as target plugin"
      • Use current directory as target plugin
    • If not found:
      • Output: "Not in a plugin directory, checking for marketplace..."

    b. If not in plugin directory, check if we're in marketplace root:

    • Look for .claude-plugin/marketplace.json in current directory
    • If found:
      • Output: "Found marketplace.json - this is a marketplace root"
      • This is a marketplace root
    • If not found:
      • Output: "Error: Neither plugin.json nor marketplace.json found"
      • Show error and exit

Read the full file on GitHub · 392 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. 2d ago First seen · 392 lines · 0 tokens per session scan A 625d19b59616

Subscribe to this mod's changes

add-skill is a command published in the GitHub repository kossakovsky/cc-plugins (3 stars, last pushed 5mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 2,945 tokens. A static security scan graded it A with 0 findings. It is 97% identical to add-skill, differing in 6 lines, and is treated as a copy.