The Agent Skills Directory

[INDIRECT_PROMPT_INJECTION]: The skill processes project-specific data from .21st/design.json and .21st/DESIGN.md to influence the agent's UI generation and modification logic.
Ingestion points: Reads configuration and design instructions from the local .21st/ directory.
Boundary markers: The skill does not define clear delimiters or "ignore previous instructions" guards when reading the design context.
Capability inventory: The agent can execute the 21st CLI for searching, generating, and reviewing code, and has the ability to modify project source files.
Sanitization: No validation or sanitization is mentioned for the content of the design files before they are used to parameterize CLI commands.
[COMMAND_EXECUTION]: The skill relies on the 21st CLI tool to perform various tasks including init, search, generate, and review. These commands interact with the local filesystem and potentially remote services.
[EXTERNAL_DOWNLOADS]: The workflow involves retrieving or installing UI components from the 21st-dev service/registry to implement interface changes.

21st-ui-build