OpenAI is quietly following up on Anthropic's 'Skills' mechanism, which could be an important signal in the Agent space. What is a 'Skill'? Simply put, it's like an 'external manual' attached to AI. You don’t need to train the model—just drop a Markdown file (detailing functionality and usage) into a folder, and the AI can 'instantly learn' the new skill. For example, company-specific coding guidelines or how to use an obscure library. It’s like plugging a USB extension into AI—plug and play. Simon Willison discovered that the latest ChatGPT and Codex CLI already have these Skills pre-installed. The most typical example is ChatGPT’s current PDF processing skill: instead of directly converting text, it follows the 'SOP' in the Skill to render the PDF into images and feed them to the visual model. This 'Prompt-as-code, file-as-skill' minimalist standard is quickly becoming the strongest consensus for expanding LLM capabilities.