A Codex skill is a directory that contains a SKILL.mdfile and optional references, assets, or scripts. Codex first reads the skill's name and description. It loads the full instructions when the task matches or you invoke the skill directly.
Qualify the bookmark
Confirm that the bookmark defines a repeatable outcome, not only an idea or result. Identify the required input, ordered steps, constraints, expected output, and stopping condition. Research missing context before you write instructions.
Use the X bookmark qualification rubric to compile, research, retain, or reject the candidate.
Create the skill directory
Create one directory for one recognizable user goal. Add a SKILL.md file with YAML frontmatter:
---
name: source-backed-workflow-review
description: Review a saved technical workflow, verify its claims, and produce a source-backed implementation checklist.
---
Use this skill when the user provides a saved workflow that needs verification.
1. Identify the claimed outcome and required inputs.
2. Separate explicit instructions from unsupported assumptions.
3. Verify material claims with primary sources.
4. Produce a checklist with sources, constraints, and stopping conditions.
Do not invent missing steps or present unverified claims as facts.Choose the Codex scope
Put a project skill in .agents/skills when the workflow belongs to one repository. Put a personal skill in~/.agents/skills when you want it available across your repositories. Codex also supports administrator and bundled system locations.
For the complete location table and current behavior, see the official Codex skills documentation.
Add supporting files
Keep the main instructions concise. Put source notes, policies, and detailed examples in references/. Add scripts only when the workflow requires deterministic computation or file processing.
source-backed-workflow-review/
├── SKILL.md
└── references/
├── source.md
└── verification-checklist.mdTest skill activation
Test the description with the following request types:
- Use a direct request that must activate the skill.
- Use an indirect request with the same goal.
- Omit required input and confirm that Codex asks for it.
- Use an adjacent request that must not activate the skill.
- Use an edge case that requires the workflow to stop.
Review before installation
Inspect every instruction and supporting file. Confirm that the skill preserves its sources, states uncertainty, and does not introduce commands that the bookmark or research did not support. XSkills ties approval to the exact package checksum so a later revision cannot reuse an earlier approval.
To inspect a complete package, download the sample X bookmark review skill. For the Claude-specific path, see how to turn X bookmarks into Claude Code skills.