Teach the agent.
Build skills that work.
Turn a good result into a process you can repeat, verify, and improve.
From the first SKILL.md to an evidence-backed delivery: visual explanations, guided practice, and a complete project.
A recipe. A continuous improvement cycle.
entrada → procedimento → saída → evidência
↑________ feedbackFrom intent to a verifiable skill.
Follow the order to build the project. Do you already know the basics? Enter through the track that solves your next difficulty.
Foundations
Turn a good result into a teachable process.
Understand what a skill teaches / Start from the approved resultExplore track →Construction
Give the skill clear work and the right level of freedom.
Build a skill with clear work / Calibrate the agent’s freedomExplore track →Verification
Swap confidence in the explanation for evidence.
Verify with evidence / Do a real visual reviewExplore track →Evolution
Reduce cost, incorporate feedback, and deliver your skill.
Compare quality, cost, and effort / Evolve and deliver your first skillExplore track →A report that proves where the numbers came from.
The main project turns a sales CSV into a weekly report, with exact calculations, input validation, and evidence. A second case follows the visual process of transforming a video into an article.
- Define input, output, and acceptance criteria.
- Write and install the skill in the project.
- Run the example and reject invalid inputs.
- Log an improvement and its regression test.
Download, run, check.
Synthetic data, with no need for a paid API to run the scripts. To test skill selection, use a Codex environment available to you. Python 3 is required for the lab; the course opens in your browser.
Study with your own pace.
Mark topics as read, flag doubts, and select excerpts from the explanations to highlight or annotate. In My learning journey, gather your notes, export a backup, and resume the last topic.
Progress measures topics marked as read; it is not a certification of mastery. Complete the exercises before opening the answers. Your notes stay in the browser and are not sent to a server.
Prerequisites: know how to open folders, edit text, and talk with an agent. YAML, Markdown, tests, and evaluation concepts are explained throughout the track.
References and editorial criteria
The six steps were adapted from the transcription provided by the video’s user How to Develop Skills in Codex Better than 99% of People. The video is the methodological reference; examples, exercises, diagrams, and the lab were developed for this course.
“Better than 99%” is the title of the source, with no statistical proof presented in this material. Names, times, and comparisons from the video are not a current table of prices nor a universal ranking of models.
Technical reference consulted in 21/09/2026: OpenAI — Build skills, for SKILL.md, scopes and triggering; OpenAI — Customization, to distinguish rules, skills, and tools. Available options depend on the version and the account.
Video index: foundations 00:15; reverse engineering 02:02; task and trigger 03:39; freedom 06:23; verification 09:10; cost and effort 12:34; bicycle 14:03; demonstration and feedback 15:33–26:16. Course duration estimates include practice; they are not measurements of students.