Updating Skills and AGENTS.md for Astra with OpenAI's Guidance

Melvin Vivas · X post · 2026-09-12 · Open on X

Topics: AI Agents, Tool Use & MCP, Prompt & Context Engineering, AI Dev Tools & Productivity · Level: intermediate

Summary

The creator is updating his Skills and AGENTS.md files for the Astra model, following OpenAI's guidance. He says he is sharing two migration prompts he runs in Codex, but the prompts are not in the post text. The main lesson: agent instruction files written for older models should be updated for new ones.

Key points

• Skills and AGENTS.md written for older models may not suit Astra.
• OpenAI has published guidance on updating them.
• The creator uses Codex to run two migration prompts that rewrite these files.
• The prompts themselves are not included in the post text.

Resources mentioned

• AGENTS.md · docs · agents.md · free
  Instruction file format that gives coding agents project context such as the tech stack, skills and MCP servers.
  Also in: Claude Code Now Reads AGENTS.md When CLAUDE.md Is Missing (Melvin Vivas on X · notes), Subagents with mixed models: a strong planner and a fast executor (Melvin Vivas on X · notes), How to Prompt GPT-6 Astra in Codex: Simpler Instructions, Leaner AGENTS.md (Melvin Vivas on X · notes), OpenAI Guide: Rethinking Skills and Prompts for GPT-6 Astra (Melvin Vivas on X · notes) and 5 more
• OpenAI's Skills/AGENTS.md migration guidance for Astra · article · developers.openai.com · free
  OpenAI's guidance on adapting skills, AGENTS.md and task prompts for GPT-6 Astra.
  Also in: OpenAI Guide: Rethinking Skills and Prompts for GPT-6 Astra (Melvin Vivas on X · notes)
• OpenAI Codex · tool · openai.com · paid
  OpenAI's coding agent. In the diagram it writes code, fixes review findings and drives the build loop. The creator also used it to make this video.
  Also in: An agent bot that installs and drives Codex on its own (Melvin Vivas on X · notes), Asking a Coder bot to install Codex (Melvin Vivas on X · notes), Sign in with ChatGPT: Setting Usage Limits for Each App (Melvin Vivas on X · notes), Codex Cloud Environments Must Be Saved & Published Before Use (Melvin Vivas on X · notes) and 240 more

Try this

• Review your Skills and AGENTS.md against OpenAI's guidance for Astra.
• Use a coding agent to run migration prompts that rewrite these files.