Reading
Hatch Pet.
Fourteen patterns from a small, complete, well-shaped Codex skill — worth reading not because pets are interesting, but because the patterns transfer to anything else you’d build as a skill.
THESIS
The Hatch Pet skill is a small, complete, well-shaped example of how to build a skill that does one thing end-to-end inside an agentic environment. It is worth reading not because pets are interesting, but because the patterns transfer to anything else you’d want to build as a skill.
OpenAI Codex shipped a Plugins / Skills marketplace, the Hatch Pet skill was published into it under Apache 2.0, and there is currently very little content explaining what good skill design looks like. There’s a window for “here is one to copy” content before the marketplace fills up.
Each pattern below is grounded in a specific source pointer. Every claim has receipts. The blog quotes source verbatim; the carousel pull-quotes it; the X thread screenshots it. Below each pattern, the “lazy version” sketches what an unpolished skill would have done instead — contrast is the fastest way to see what good looks like.