The Agent Skills Directory

[COMMAND_EXECUTION]: The skill uses shell commands via 21st and npx to manage UI components, such as 21st add for installation and 21st publish for uploading local code.
[EXTERNAL_DOWNLOADS]: The skill instructs the agent to install the @21st-dev/cli package and associated dependencies from the npm registry and fetches component code from the official 21st.dev registry.
[CREDENTIALS_UNSAFE]: The skill manages authentication by reading from ~/.config/21st/auth.json and supports passing API keys via standard environment variables like TWENTYFIRST_TOKEN or API_KEY_21ST.
[INDIRECT_PROMPT_INJECTION]: The skill possesses an indirect prompt injection surface as it downloads external React component code (21st add) and processes user-provided descriptions for AI generation (21st generate). While no explicit sanitization or boundary markers are documented, the capabilities are restricted to the local development environment and the 21st.dev platform.

21st-cli