Compare
Codex CLI vs Claude API
Side-by-side comparison of Codex CLI and Claude API for SKILL.md agent skills — install model, shell access, native support, skill count and best use cases.
Comparison
At a glance
| Dimension | Codex | Claude API |
|---|---|---|
| Vendor | OpenAI | Anthropic |
| Native SKILL.md support | Yes | Yes |
| Verified skills indexed | 45 | 13 |
| Install model | Local folder | POST /v1/skills |
| Shell / Bash access | Yes | Sandboxed |
| Tagline | OpenAI's coding agent CLI. Adopted the SKILL.md spec verbatim in Dec 2025. | Claude API + Skills SDK. Pre-built skill_id values plus custom uploads via /v1/skills. |
Both
9
Skills verified to work on both Codex and Claude API.
Only Codex
36
Indexed for Codex CLI but not yet verified on Claude API.
Only Claude API
4
Indexed for Claude API but not yet verified on Codex CLI.
Verdict
Which should you pick?
Both support SKILL.md natively, so the choice is about ecosystem fit. Pick Codex CLI for OpenAI integrations and the workflows it makes easiest; pick Claude API for Anthropic integrations and its specific surface.
Many teams use both — Skills with the SKILL.md spec are portable, and 9 of the skills indexed here are verified on both agents. Browse the per-agent rankings to see which Skills lead on each platform: Skills for Codex CLI · Skills for Claude API.
FAQ
Common questions
Which is better for SKILL.md skills, Codex CLI or Claude API?
Both support SKILL.md natively. Codex CLI has 45 verified skills indexed here; Claude API has 13. 9 skills work on both.
Can I use the same Skill on Codex CLI and Claude API?
9 of the skills indexed here work on both. The SKILL.md spec is shared, so most skills run cleanly on both — the exceptions are skills that depend on agent-specific tools (Bash, Workflows, MCP patterns).
How do I install a Skill on Codex CLI?
Drop the Skill folder under `~/.codex/skills/` for user-wide or `.codex/skills/` for project-scoped. Codex loads SKILL.md the same way Claude Code does.
How do I install a Skill on Claude API?
POST your Skill zip to /v1/skills. You receive a skill_id. Reference it in your messages request — the model loads the Skill on demand.
Which agent should I pick for cross-platform skill use?
Both support skills natively. Pick by ecosystem fit: Codex CLI for OpenAI customers, Claude API for Anthropic customers.
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