Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add 21st-dev/codex-plugin --skill 21st-aigit clone --depth 1 https://github.com/21st-dev/codex-pluginWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/21st-dev/codex-plugin/21st-ai)<a href="https://agentmods.dev/skills/21st-dev/codex-plugin/21st-ai"><img src="https://agentmods.dev/badge/skills/21st-dev/codex-plugin/21st-ai/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/21st-dev/codex-plugin/21st-ai"><img src="https://agentmods.dev/badge/skills/21st-dev/codex-plugin/21st-ai.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00195 | $0.01348 |
| Opus 5.5 | $0.00078 | $0.00539 |
| Sonnet 5.5 | $0.00039 | $0.00270 |
| Haiku 4.5 | $0.00019 | $0.00135 |
Grade A, and why
21st-ai scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
100% identical to 21st-ai — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 107 lines — stays where its author put it; the contents beside it link to each section on GitHub.
21st AI — sketch, iterate & grab code from the terminal
21st AI is a fast UI-drafting board. Mental model: draft it here, then finish
it — sketch a few variants from a prompt, preview them, refine the one you like
with plain-English edits, and pull its code into the repo. The whole loop runs
from the 21st CLI (or the matching MCP tools), so you never leave the editor.
Sketch mode produces self-contained HTML + Tailwind drafts (fast, no build). The recommended handoff is the copy-prompt: a spec that tells you to rebuild the design in the target project's real stack — not paste raw HTML verbatim.
Auth
Same credential as the rest of the CLI: 21st login (saved token) or a
21st_sk_ key via --api-key / TWENTYFIRST_TOKEN. 21st usage (MCP:
get_usage) shows the account tier, aiGenerationEnabled, and remaining free
daily component-code retrieval quota. It does not report the AI credit balance.
(See the 21st-cli-use skill for the full auth notes.)
Before generating or iterating, check MCP get_usage.aiGenerationEnabled or
the 21st AI generation line from 21st usage. CLI 1.17.1 also supports
21st usage --json. Proceed only when AI is explicitly enabled; missing or
unknown status does not grant access. A base Builder
subscription does not enable AI. When it is false, use search →
get_component and adapt the code with the user's own agent. Do not attempt
generate or iterate_generation, including through the CLI as a fallback.
The loop
# 1) Sketch — generate variants ("takes") from a prompt. Opens the preview in
# the browser and prints the projectId.
21st generate "a pricing section with 3 tiers and a monthly/annual toggle"
# 2) List the takes (1-based numbers + whether each has rendered yet).
21st generation <projectId>
# 3) Edit ONE take in place with a natural-language change (PAID — see Metering).
21st iterate <projectId> "make it enterprise-flavored, add an annual toggle" --take 3
# 4) Grab the code to bring into the project (FREE).
21st take <projectId> --take 3 # paste-ready copy-prompt (recommended)
21st take <projectId> --take 3 --code # raw self-contained HTML instead
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago Changed · +17 lines 229119802d83
- 1mo ago First seen · 90 lines · 195 tokens per session scan A bc928af4cd81
21st-ai is a skill published in the GitHub repository 21st-dev/codex-plugin (10 stars, last pushed 10d ago), licensed Apache-2.0. It adds 195 tokens to every session and 1,348 once invoked, about $0.0008 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to 21st-ai, differing in 0 lines, and is treated as a copy.
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