PlantUML Syntax Reference Skill

PlantUML Syntax Reference

Overview

PlantUML is a Java-based tool that creates diagrams from text descriptions. It supports comprehensive UML diagrams and many non-UML diagram types.

Key advantages:

Most comprehensive diagram support (15+ types)
Mature C4 model integration with icons/sprites
Extensive customization options
Battle-tested (since 2009)

Requirements:

Java Runtime Environment (JRE)
GraphViz (for some diagram types)
Or use Docker: docker run -p 8080:8080 plantuml/plantuml-server

Diagram Types Quick Reference

UML Diagrams

| Type | Keywords | Best For | | --- | --- | --- | | Sequence | @startuml | Interactions, API flows, protocols | | Use Case | @startuml | Requirements, user stories | | Class | @startuml | OOP design, domain models | | Activity | @startuml | Workflows, processes | | Component | @startuml | System structure | | Deployment | @startuml | Infrastructure, deployment | | State | @startuml | State machines |

Non-UML Diagrams

| Type | Keywords | Best For | | --- | --- | --- | | JSON | @startjson | JSON structure visualization | | YAML | @startyaml | YAML structure visualization | | Wireframe | @startsalt | UI mockups | | Gantt | @startgantt | Project timelines | | MindMap | @startmindmap | Hierarchical ideas | | WBS | @startwbs | Work breakdown | | ER | @startuml | Database schemas | | C4 | @startuml with C4 include | Software architecture |

Basic Syntax

All PlantUML diagrams are wrapped in start/end tags:

@startuml
' Your diagram code here
@enduml

Comments:

Single line: ' This is a comment
Block: /' This is a block comment '/

Title and captions:

@startuml
title My Diagram Title
caption This is a caption
header Page Header
footer Page Footer

' Diagram content
@enduml

Quick Reference Card

Sequence

@startuml
participant A
participant B
A -> B: Message
A <-- B: Response
@enduml

Class

@startuml
class Name {
    - private
    + public
    + method()
}
A <|-- B : extends
A *-- B : contains
@enduml

Activity

@startuml
start
:Action;
if (condition?) then (yes)
    :True path;
else (no)
    :False path;
endif
stop
@enduml

State

@startuml
[*] --> State1
State1 --> State2 : event
State2 --> [*]
@enduml

Component

@startuml
[Component1] --> [Component2]
database DB
Component2 --> DB
@enduml

References

For detailed syntax and complete examples, see:

| Reference | Content | When to Load | | --- | --- | --- | | sequence.md | Participants, arrows, activation, groups, notes | Creating sequence diagrams | | class.md | Classes, visibility, relationships, cardinality | Creating class diagrams | | activity.md | Conditions, swimlanes, fork/join | Creating activity diagrams | | state-component.md | State machines, components, deployment | Creating state/component diagrams | | c4.md | C4 context, container, component diagrams | Creating C4 architecture diagrams | | special-diagrams.md | ER, JSON, MindMap, Gantt | Creating non-UML diagrams | | styling-setup.md | Skinparams, themes, installation | Customizing diagrams, setting up PlantUML |

File Extensions

| Extension | Description | | --- | --- | | .puml | Standard PlantUML file | | .plantuml | Alternative extension | | .pu | Short extension | | .iuml | Include file |

Test Scenarios

Scenario 1: Creating a sequence diagram

Query: "Create a PlantUML sequence diagram for user authentication"

Expected: Skill activates, provides sequence syntax with participants, arrows, and alt/else blocks

Scenario 2: Creating a class diagram

Query: "Generate a PlantUML class diagram for an e-commerce domain"

Expected: Skill activates, provides class syntax with relationships and cardinality

Scenario 3: Creating a C4 diagram

Query: "Create a C4 container diagram in PlantUML"

Expected: Skill activates, directs to c4.md reference for includes and syntax

Last Updated: 2025-12-28 PlantUML Version: 1.2024.6

Version History

v1.1.0 (2025-12-28): Refactored to progressive disclosure - extracted content to references/
v1.0.0 (2025-12-26): Initial release

Agent Skills: PlantUML Syntax Reference

Install this agent skill to your local

Skill Files