Codex Subagents: Attaching Skills and MCP Servers per Subagent

Melvin Vivas · X post · 2026-09-08 · Open on X

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

Summary

In OpenAI Codex's subagent configuration, you can set Skills and MCP servers for each subagent separately, not just globally. The creator is testing a frontend subagent with a design skill to replace a separate design tool (Claude Design), and asks for good design skills to try.

Key points

• Codex subagent config lets you set Skills per subagent
• MCP servers can also be set per subagent
• Pattern: give a specialized subagent (e.g. frontend) its own domain skill, such as a design skill
• Scoping tools and skills per subagent can stand in for separate specialized products

Resources mentioned

• 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
• Claude Design · tool · anthropic.com · paid
  Anthropic Labs tool that creates prototypes, slides and one-pagers when you describe them to Claude in chat.
  Also in: Improving Codex's UI Design Output with Impeccable (npx impeccable install) (Melvin Vivas on X · notes), AutoDesign: Improving the Harness Around the Model with a Meta-Harness Loop (Melvin Vivas on X · notes), Claude Code's /design Skill: Pick UI Artboards, Then Have Claude Build One (Melvin Vivas on X · notes), Claude Design Is Now in the Claude Desktop App (Melvin Vivas on X · notes) and 4 more

Try this

• Set up a frontend subagent in Codex with a design skill and the MCP servers it needs
• Build a frontend subagent in Codex with its own design skill and MCP tools