---
title: "Agent Skills Marketplace - Claude, Codex & ChatGPT Skills"
url: https://stacklist.com/card/6575732a-ff40-48d4-bf0a-969e690fb523
source_url: "https://skillsmp.com/"
stack: https://stacklist.com/stack/adf42802-57ae-4bec-810c-7ec6565a3b86
summary: "Agent Skills are modular capabilities that extend AI coding assistants, consisting of a SKILL.md file with instructions plus optional scripts and templates. In December 2025, Anthropic released the Agent Skills specification as an open standard, which OpenAI adopted for Codex CLI and ChatGPT."
tags: "agent-skills, ai-coding-assistants, modular-capabilities, anthropic, openai, specification, codex"
key_entities: "Agent Skills (technology), Anthropic (organization), OpenAI (organization), Codex CLI (technology), ChatGPT (technology), AI coding assistants (concept), Agent Skills specification release (event)"
classification: "reference"
content_hash: "sha256:6e5229d4d0711d7e122a4223bb0303fdd42bd08504445c609373cc8a0f41ea60"
acp_version: "0.2"
token_counts_approximate: 112
visibility: public
agent_accessible: true
status: "final"
---

# Agent Skills Marketplace - Claude, Codex & ChatGPT Skills

01 Q: What are Agent Skills? [+] /** * Agent Skills are modular capabilities that extend AI coding assistants. Each skill consists of a SKILL.md file with instructions, plus optional scripts and templates. In December 2025, Anthropic released the Agent Skills specification as an open standard, and OpenAI adopted the same format for Codex CLI and ChatGPT. Skills are model-invoked—the AI automatically decides when to use them based on context. */