---
title: Claude API vs Codex CLI
slug: claude-api-vs-codex
type: agent-comparison
a: claude-api
b: codex
canonical: https://top-agent-skills.com/compare/claude-api-vs-codex
rubric: 1.0
---

# Claude API vs Codex CLI

Side-by-side for SKILL.md agent Skills: install model, shell access, native support, and how many Skills are verified on each.

## At a glance

| | Claude API | Codex |
| --- | --- | --- |
| Vendor | Anthropic | OpenAI |
| Native SKILL.md support | Yes | Yes |
| Verified skills indexed | 13 | 55 |
| Install model | POST /v1/skills | Local folder |
| Shell / Bash access | Sandboxed | Yes |
| Tagline | Claude API + Skills SDK. Pre-built skill_id values plus custom uploads via /v1/skills. | OpenAI's coding agent CLI. Adopted the SKILL.md spec verbatim in Dec 2025. |

## Overlap

- Verified on both: 9
- Only Claude API: 4
- Only Codex: 46

## Which should you pick?

Both support SKILL.md natively, so the choice is about ecosystem fit. Pick Claude API for Anthropic integrations and the workflows it makes easiest; pick Codex CLI for OpenAI 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.

Per-agent rankings: https://top-agent-skills.com/skills-for-claude-api · https://top-agent-skills.com/skills-for-codex

## Common questions

**Which is better for SKILL.md skills, Claude API or Codex CLI?**

Both support SKILL.md natively. Claude API has 13 verified skills indexed here; Codex CLI has 55. 9 skills work on both.

**Can I use the same Skill on Claude API and Codex CLI?**

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 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.

**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.

**Which agent should I pick for cross-platform skill use?**

Both support skills natively. Pick by ecosystem fit: Claude API for Anthropic customers, Codex CLI for OpenAI customers.

---

_Top Agent Skills. Machine-readable twin of https://top-agent-skills.com/compare/claude-api-vs-codex._