antoinebou12/uml-mcp-diagrams

uml-mcp diagram workflow

Goal

Turn the user’s intent into valid diagram_type + source code, call generate_uml, and surface the url (and playground when present). Prefer URL-only output unless the user explicitly asks to save a file.

Before generating

1. If diagram_type is unknown or ambiguous, read the uml://types resource (or uml://capabilities) to list valid types and supported backends.
2. For starter syntax, use uml://templates or uml://examples; for Mermaid specifics, uml://mermaid-examples when relevant.
3. Optional quality pass: call validate_uml with the same diagram_type, code, and planned output_format to catch local errors before render. Use strict: true for stricter Mermaid/D2 checks when needed.
4. If you cannot read uml://types, call list_diagram_types for the same metadata.

Calling generate_uml

| Input | Guidance | |-------|----------| | diagram_type | Required. Must match a key from uml://types (e.g. class, sequence, mermaid, d2). | | code | Required. Source in the language that matches diagram_type. | | output_dir | Omit or null for URL / base64 only (no write to disk). Set only if the user wants a saved image. | | output_format | Default svg is usually best for URLs; use png/pdf/jpeg/txt only if valid for that type (see uml://formats). | | theme | PlantUML types only; omit otherwise. | | scale | SVG only; optional size multiplier. |

After generating

1. If the result includes error, fix code or diagram_type / output_format and retry (or run validate_uml again).
2. Present clearly:
   • url — primary Kroki link to the rendered diagram.
   • playground — if present, link for interactive editing.
   • local_path — only when output_dir was set.
3. Keep a short copy of the code in the reply so the user can edit and regenerate.

Choosing a language from intent

| User intent | Typical diagram_type | |-------------|------------------------| | Classes, associations, packages | class (PlantUML) or mermaid with classDiagram | | Messages over time, lifelines | sequence or Mermaid sequence | | Flows, swimlanes, BPMN | activity, bpmn, or Mermaid flowchart | | Components, deployment | component, deployment, or C4-style types if listed in uml://types | | Quick graphs, Gantt, pie | mermaid | | Declarative layout / modern DSL | d2 |

When several types fit, pick the one the user named; otherwise prefer the type with the clearest template in uml://templates.

MCP tools and resources

• Tools: generate_uml, validate_uml, list_diagram_types, generate_uml_batch
• Resources: uml://types, uml://formats, uml://templates, uml://examples, uml://capabilities, uml://server-info, uml://mermaid-examples, uml://bpmn-guide, uml://workflow

Prompts (when the client exposes them): uml_diagram, uml_diagram_with_thinking, and type-specific prompts (class_diagram, sequence_diagram, activity_diagram, usecase_diagram, mermaid_sequence_api, mermaid_gantt, bpmn_process_guide, c4_model, wireviz_harness, bpmn_executable_process, convert_class_to_mermaid) help structure code before generate_uml.

Always use the MCP tool/resource APIs exposed in the environment; do not guess unsupported diagram_type or output_format values when unsure—confirm with uml://types / uml://formats.