Skip to content

PlantUML prompts and SVG

Use this track when you want UML-style diagrams (classes, sequences, activities, use cases) rendered by PlantUML through Kroki. For syntax details and more examples, see UML (PlantUML).

Prerequisites

  • A connected UML-MCP server (Getting started).
  • Optional: a Sequential Thinking MCP server in the same client (for example Cursor) if you want explicit multi-step reasoning before calling generate_uml. It is not part of UML-MCP; it complements uml_diagram_with_thinking, which is a named prompt on UML-MCP only.

Natural-language prompts (copy-paste)

Ask your assistant in plain language, then let it fetch uml://types / uml://workflow and call tools:

Draw a PlantUML class diagram for a small library: Book, Copy, Member, Loan.
Book has title and isbn. Member has id and name. Loan links a Member to a Copy with dueDate.
A Book has many Copies. A Member can have many active Loans.

Produce a PlantUML sequence diagram: Client calls POST /orders, API validates payload,
writes to Orders DB, publishes OrderCreated to a message queue, returns 201 with order id.
Include alt: validation failure returns 400.

Activity diagram (PlantUML): start, read config file, if valid parse else show error,
if parse ok run pipeline then end; on pipeline error log and end.

Use case diagram: Actor Librarian manages catalog; Actor Member searches and borrows;
system boundary LibrarySystem; include relationship SearchCatalog from Borrow to Search.

Example Sequential Thinking flow (then generate_uml)

Illustrative steps you might run through the Sequential Thinking tool before generating:

  1. Scope: Static structure only (classes + associations), no sequence.
  2. Notation: PlantUML class with @startuml / @enduml, visibility optional.
  3. Entities: Account, Customer, one-to-many Customer to Account.
  4. Risks: Avoid ambiguous navigability; name associations clearly.
  5. Validation: Call validate_uml with diagram_type: class and the same source, then generate_uml with "output_format": "svg".

Then call generate_uml with diagram_type set to a PlantUML-backed type (for example class, sequence, or raw plantuml), your final source as code, "output_format": "svg", and omit output_dir (or set it to null) if you only need a URL or content_base64 without writing a file.

Named MCP prompts (UML-MCP)

Prompt Use when
uml_diagram Generic plan-then-generate for any supported type.
uml_diagram_with_thinking Same, with an explicit planning step before code.
class_diagram Class diagram from prose.
sequence_diagram Sequence diagram from prose.
activity_diagram Activity / workflow from prose.
usecase_diagram Use case diagram from prose.

Fetch text with prompts/get (see MCP prompts).

Direct tools/call (JSON-RPC)

Minimal example for the diagram below (same source as the committed SVG):

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "generate_uml",
    "arguments": {
      "diagram_type": "class",
      "output_format": "svg",
      "code": "@startuml\nclass Account {\n  +String id\n  +String owner\n}\nclass Customer {\n  +String name\n}\nCustomer \"1\" --> \"*\" Account\n@enduml"
    }
  }
}

Example output (server-rendered SVG)

This asset was produced with UML-MCP generate_uml (diagram_type: class, output_format: svg) and the same code as above.

PlantUML class diagram example