core-agent-ide/docs/skills.md

Skills (experimental)

Warning: This is an experimental and non-stable feature. If you depend on it, please expect breaking changes over the coming weeks and understand that there is currently no guarantee that this works well. Use at your own risk!

Codex can automatically discover reusable "skills" you keep on disk. A skill is a small bundle with a name, a short description (what it does and when to use it), and an optional body of instructions you can open when needed. Codex injects only the name, description, and file path into the runtime context; the body stays on disk.

Where skills live

• Location (v1): ~/.codex/skills/**/SKILL.md (recursive). Hidden entries and symlinks are skipped. Only files named exactly SKILL.md count.
• Sorting: rendered by name, then path for stability.

File format

• YAML frontmatter + body.
  • Required:
    • name (non-empty, ≤100 chars, sanitized to one line)
    • description (non-empty, ≤500 chars, sanitized to one line)
  • Extra keys are ignored. The body can contain any Markdown; it is not injected into context.

Loading and rendering

• Loaded once at startup.
• If valid skills exist, Codex appends a runtime-only ## Skills section after AGENTS.md, one bullet per skill: - <name>: <description> (file: /absolute/path/to/SKILL.md).
• If no valid skills exist, the section is omitted. On-disk files are never modified.

Validation and errors

• Invalid skills (missing/invalid YAML, empty/over-length fields) trigger a blocking, dismissible startup modal in the TUI that lists each path and error. Errors are also logged. You can dismiss to continue (invalid skills are ignored) or exit. Fix SKILL.md files and restart to clear the modal.

Create a skill

1. Create ~/.codex/skills/<skill-name>/.

2. Add SKILL.md:

   ---
   name: your-skill-name
   description: what it does and when to use it (<=500 chars)
   ---
   
   # Optional body
   Add instructions, references, examples, or scripts (kept on disk).
   

3. Keep name/description within the limits; avoid newlines in those fields.

4. Restart Codex to load the new skill.

Example

mkdir -p ~/.codex/skills/pdf-processing
cat <<'SKILL_EXAMPLE' > ~/.codex/skills/pdf-processing/SKILL.md
---
name: pdf-processing
description: Extract text and tables from PDFs; use when PDFs, forms, or document extraction are mentioned.
---

# PDF Processing
- Use pdfplumber to extract text.
- For form filling, see FORMS.md.
SKILL_EXAMPLE