Codex CLI has moved beyond simple prompt injection. The new architecture treats agent capabilities as filesystem objects. A skill is just a folder containing a SKILL.md file. This file defines the agent's behavior for specific tasks like code review or feature planning. The CLI discovers these skills automatically from .agents/skills/ in your repo or ~/.agents/skills/ for user-level configurations. This local-first approach mirrors the OpenClaw philosophy: keep the context close to the code.

The Anatomy of a Codex Skill

You don't need a complex plugin system. A valid skill requires a SKILL.md with YAML frontmatter. It needs a name, a description, and actionable instructions. For example, a 'review-brief' skill might instruct Codex to list missing requirements and propose acceptance criteria. Once placed in the correct directory, you invoke it with /skills or the $ prefix. The agent selects the skill based on its description if you don't explicitly call it. This simplicity is the point. It removes the friction of context switching.

Bridging to Hosted Capabilities with SkillGild

Local skills are great for static instructions, but what about dynamic, hosted capabilities? That's where the SkillGild CLI enters the stack. You install the CLI, which currently requires Go 1.26 or later. After signing in with skillgild login, you register a local MCP server using codex mcp add. This creates a stdio bridge between Codex and the SkillGild backend. You don't paste API keys into Codex's config. The credential lives in your OS store. It's a clean separation of concerns.

Hybrid Workflows and Wrapper Installation

Installing a hosted skill like 'design-taste-frontend' doesn't copy the private implementation to your machine. Instead, skillgild install writes a wrapper SKILL.md to ~/.agents/skills/. When you invoke it, Codex uses its own model for the session guide but calls SkillGild's server tools via skillgild_run_skill. This hybrid model allows for protected capabilities without exposing proprietary logic. If a call fails, check codex mcp list and skillgild status separately. Discovery and connectivity are two different failure modes. Don't confuse them.

Key Takeaways

  • Codex skills are local folders with SKILL.md files, discovered via .agents/skills/ or ~/.agents/skills/.
  • The SkillGild CLI acts as an MCP bridge, requiring Go 1.26+ and OS-level credential storage.
  • Hosted skills use wrappers that delegate specific tool calls to remote servers while keeping session logic local.
  • Troubleshooting requires separating skill discovery issues from MCP server connectivity failures.

The Bottom Line

This isn't just a tutorial; it's a blueprint for agent interoperability. By standardizing on SKILL.md and MCP, Codex CLI avoids vendor lock-in. You can swap backends without rewriting your workflow. That's real hacker culture: portable, modular, and transparent.