MCP Tools Reference¶

generate_uml renders diagrams and can save to disk. validate_uml checks inputs locally without calling Kroki. list_diagram_types returns the same metadata as the uml://types resource. generate_uml_batch renders several diagrams in one call (see Configuration for MCP_BATCH_MAX_ITEMS). For diagram types and formats, use uml://types and uml://formats.

Rendering fallback¶

The server tries Kroki first. If Kroki fails or is unreachable, the pipeline can use a PlantUML server (see PLANTUML_SERVER and USE_LOCAL_PLANTUML in Configuration) or Mermaid.ink for Mermaid diagrams. Successful responses may include a source field (kroki, plantuml_server, or mermaid_ink) naming the backend that produced the image.

generate_uml¶

Generates a diagram. Pass output_dir only when you need a file on disk; if you omit it, you get url, playground, and content_base64 (no file write). On read-only deployments (MCP_READ_ONLY=true), output_dir is rejected; omit it and use URL/base64 only.

Parameters:

• diagram_type (string): Supported type (class, sequence, mermaid, d2, tikz, bpmn, graphviz, etc.). See uml://types.
• code (string): Diagram source in the syntax for that type.
• output_dir (string, optional): Directory to write the image. Omit for URL/base64 only.
• output_format (string, optional): svg, png, pdf, jpeg, txt, or base64 (default: svg). Allowed values depend on the diagram type; see uml://formats.
• theme (string, optional): PlantUML theme (e.g. cerulean) for PlantUML-based types.
• scale (number, optional): Scale factor for SVG only (default: 1.0, min: 0.1). Ignored for png, pdf, jpeg, etc.

Returns JSON with code, url, playground; local_path when output_dir was set; content_base64 when not saving; or error on failure.

Example (save to disk):

{
  "type": "tool",
  "name": "generate_uml",
  "args": {
    "diagram_type": "class",
    "code": "@startuml\nclass User\n@enduml",
    "output_dir": "./output"
  }
}

Example (URL / base64 only):

{
  "type": "tool",
  "name": "generate_uml",
  "args": {
    "diagram_type": "mermaid",
    "code": "graph TD; A-->B;"
  }
}

list_diagram_types¶

Returns a JSON object whose keys are diagram type names and whose values include backend, description, and formats (same as uml://types). No parameters.

generate_uml_batch¶

Parameters:

• items (array of objects): each object supports the same fields as generate_uml except output_dir (not per item). Required: diagram_type, code. Optional: output_format, theme, scale.
• output_dir (string, optional): shared output directory for all items; omit for URL/base64 only.

Returns { "results": [ { "index": 0, ... }, ... ] } where each entry matches generate_uml output or includes error for that index. Empty items or exceeding MCP_BATCH_MAX_ITEMS yields an error at the top level.

validate_uml¶

Validates diagram_type, code, and output_format locally (no network). Use before generate_uml to catch unsupported types or formats.

Parameters: diagram_type, code, output_format (default svg), strict (boolean, default false). When true, applies extra Mermaid/D2 checks only (no extra PlantUML rules beyond existing @startuml/@enduml balance).

TikZ support¶

For diagram_type: "tikz", code is TikZ/LaTeX source. You can pass a snippet (e.g. \begin{tikzpicture}...\end{tikzpicture}) or a full document; snippets are wrapped in a minimal standalone document. Supported output formats: svg, pdf, png, jpeg. Common TikZ libraries (e.g. shapes, arrows, positioning, pgfplots, automata) are inferred when possible. See TikZ diagrams for templates and examples.

Example (TikZ):

{
  "type": "tool",
  "name": "generate_uml",
  "args": {
    "diagram_type": "tikz",
    "code": "\\\\begin{tikzpicture}\\\\draw (0,0) circle (1cm);\\\\end{tikzpicture}",
    "output_format": "svg"
  }
}