Skill Development

A guide for creating skills for Copilot CLI plugins. Skills are instruction packages that give a coding assistant specialized workflows, knowledge, tools, and supporting files.

In plain words
What is it for?
Use it to create or improve SKILL.md files, write skill descriptions and triggers, organize scripts or reference files, and validate plugin skill packages.
Why use it?
It helps authors structure skills consistently so they are easier for the assistant to discover, follow, validate, and maintain.

Skill for Claude CodeCodex

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 skills/poorgramer-zack/copilot-cli-things/skill-development
Any agent
npx skills add Poorgramer-Zack/copilot-cli-things --skill skill-development
Clone the repo
git clone --depth 1 https://github.com/Poorgramer-Zack/copilot-cli-things

Made for: Claude Code, Codex.

Per session 56 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,998 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 86% 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 $0.00056 $0.04998
Opus 5 $0.00028 $0.02499
Sonnet 5 $0.00011 $0.01000
Haiku 4.5 $0.00006 $0.00500

Measured 2d ago against content hash eea1fd08ee8f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

Skill Development 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

86% identical to Skill Development — 60 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-dev/skills/skill-development/SKILL.md · 632 lines

How it starts

The opening of the file, as written. The whole thing — 632 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill Development for Copilot CLI Plugins

Create effective skills for Copilot CLI plugins following best practices for structure, progressive disclosure, and trigger matching.

About Skills

Skills are modular, self-contained packages that extend Copilot's capabilities with specialized knowledge, workflows, and tools — "onboarding guides" that transform Copilot from a general-purpose agent into a domain-specialized agent with procedural knowledge no model fully possesses.

What Skills Provide

  1. Specialized workflows - Multi-step procedures for specific domains
  2. Tool integrations - Instructions for working with specific file formats or APIs
  3. Domain expertise - Company-specific knowledge, schemas, business logic
  4. Bundled resources - Scripts, references, and assets for complex and repetitive tasks

Anatomy of a Skill

Every skill consists of a required SKILL.md file and optional bundled resources:

skill-name/
├── SKILL.md (required)
│   ├── YAML frontmatter metadata (required)
│   │   ├── name: (required)
│   │   └── description: (required)
│   └── Markdown instructions (required)
└── Bundled Resources (optional)
    ├── scripts/          - Executable code (Python/Bash/etc.)
    ├── references/       - Documentation intended to be loaded into context as needed
    └── assets/           - Files used in output (templates, icons, fonts, etc.)
SKILL.md (required)

Metadata Quality: The name and description in YAML frontmatter determine when Copilot will use the skill. Be specific about what the skill does and when to use it. Use the third-person (e.g. "This skill should be used when..." instead of "Use this skill when...").

Bundled Resources (optional)
Scripts (scripts/)

Executable code (Python/Bash/etc.) for tasks that require deterministic reliability or are repeatedly rewritten.

  • When to include: When the same code is being rewritten repeatedly or deterministic reliability is needed
  • Example: scripts/rotate_pdf.py for PDF rotation tasks
  • Benefits: Token efficient, deterministic, may be executed without loading into context
  • Note: Scripts may still need to be read by Copilot for patching or environment-specific adjustments

Read the full file on GitHub · 632 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 · 632 lines · 56 tokens per session scan A eea1fd08ee8f

Subscribe to this mod's changes

Skill Development is a skill published in the GitHub repository Poorgramer-Zack/copilot-cli-things (2 stars, last pushed 5mo ago), licensed MIT. It adds 56 tokens to every session and 4,998 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 86% identical to Skill Development, differing in 60 lines, and is treated as a copy.

Related

Other skills, from other repositories

retrospective

Stage A of /prflow:retrospective-weekly: analyze one non-clean PR from its pre-fetched context bundle and return a retrospective entry as JSON. Invoked as a subagent — do not call it directly.

The01Geek/prflow · 50 tokens

subagent-governance

Delegation admissibility governance for a parent orchestrator. Use when deciding whether to launch, sequence, replace, or accept one or more delegated child runs while preserving role fit, plan-backed worker contracts, one-writer isolation, bounded retry safety, and reviewer finding disposition. Covers admissibility…

Firstp1ck/pi-coding-agent-forge · 74 tokens

skill-creator

Use when you want to create a new SKILL.md file — describe a workflow and this skill generates a properly structured, frontmatter-complete SKILL.md that follows this repository's conventions.

drvoss/everything-copilot-cli · 41 tokens

Skill Builder

Create new Claude Code Skills with proper YAML frontmatter, progressive disclosure structure, and complete directory organization. Use when you need to build custom skills for specific workflows, generate skill templates, or understand the Claude Skills specification.

aegntic/cldcde · 46 tokens

speckit-init

Scaffold a Spec Kit (spec-driven development) project for GitHub Copilot by running specify init --integration copilot --integration-options="--skills". USE FOR: starting a new spec-kit project, bootstrapping spec-driven development in an existing repo, installing spec-kit templates/scripts/commands for Copilot. DO…

github/spec-kit-copilot · 113 tokens

speckit-bundle

Discover, install, and author Spec Kit bundles via specify bundle. USE FOR: searching/showing/listing bundles, installing/updating/removing a bundle (a curated set of extensions/presets/integrations/workflows), validating a bundle manifest, building a distributable bundle artifact, initializing a project and…

github/spec-kit-copilot · 99 tokens