Plantuml Skill

This is a zero-install diagramming tool that uses PlantUML syntax and renders through the Kroki cloud API, so you just need curl. It handles sequence diagrams, component architecture, class models, ER schemas, and about a dozen other UML types. The skill knows to activate proactively when you're explaining systems with multiple moving parts, which is actually useful instead of waiting to be asked. The syntax reference is thorough and includes real color codes and arrow types. If you're offline or don't trust the cloud, it falls back to local Kroki Docker or a traditional PlantUML jar setup. Much faster than fighting with Graphviz installation issues.