staruml-mcp

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create_diagram

Create a typed UML diagram in StarUML, like class or sequence diagrams, providing an empty native canvas to populate with elements via create_element.

Instructions

Create a typed UML diagram. The 'type' is a metamodel class name (e.g. 'UMLClassDiagram', 'UMLUseCaseDiagram', 'UMLSequenceDiagram', 'UMLActivityDiagram', 'ERDDiagram'). Unlike generate_diagram (Mermaid), this gives a native empty diagram you can populate via create_element. Requires staruml-mcp-extension to be installed in StarUML. Install from https://github.com/ezrabrilliant/staruml-mcp-extension

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "type": "<type>",
      "parentId": "<parentId>"
    },
    "name": "create_diagram"
  }
}

Input Schema

Name	Required	Description
`name`	No	Diagram name
`type`	Yes	Diagram metamodel type: 'UMLClassDiagram', 'UMLUseCaseDiagram', 'UMLSequenceDiagram', 'UMLActivityDiagram', 'UMLStateDiagram', 'UMLComponentDiagram', 'UMLDeploymentDiagram', 'ERDDiagram'
`parentId`	Yes	Parent element's _id (usually the project or a package)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.3.3Jul 28, 2026

TDQS

A4.3/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries full burden. It discloses that the tool requires the staruml-mcp-extension and that the created diagram is empty and can be populated via create_element. It does not discuss side effects, error states, or return values, but the behavioral information provided is substantive and actionable.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences plus an install link, with the core purpose in the first sentence. Every word is necessary; no fluff. The front-loaded structure immediately conveys the tool's function.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the three parameters (all described), no output schema, and no annotations, the description adequately covers purpose, type explanation, and prerequisites. However, it omits what the return value is (e.g., the created diagram ID) and does not mention error conditions. This leaves the agent slightly under-informed for a creation tool.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, but the description adds value by explaining that 'type' is a metamodel class name with example values, and clarifies parentId as the parent element's _id (usually project or package). This goes beyond the schema's brief descriptions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description starts with 'Create a typed UML diagram,' a specific verb and resource. It distinguishes itself from the sibling tool generate_diagram by clarifying that this creates a native empty diagram vs. Mermaid-based generation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly contrasts with generate_diagram ('Unlike generate_diagram (Mermaid), this gives a native empty diagram you can populate via create_element'), providing clear context for when to choose this tool. However, it does not mention when not to use it or other potential alternatives among the siblings.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.