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Diagram Assistant

This page lists the MCP tools, resources, and prompts for generating and reading UML and other diagram types. The table maps four example user prompts to the tools and resources the server uses.

Example prompts and behavior

User prompt Desired behavior Tools Resources
"Show me a Mermaid sequence diagram for an API call" Return valid Mermaid sequenceDiagram (client → API → backend) and optionally call generate_uml("mermaid", code). generate_uml uml://examples (mermaid); see Mermaid for sequence API sample text
"Generate a Gantt chart using Mermaid syntax" Return valid Mermaid gantt block and optionally call generate_uml("mermaid", code). generate_uml uml://templates (mermaid), Mermaid (Gantt sample)
"Explain how to draw a BPMN process model" Return concise guidance (elements, flow, BPMN 2.0.2 alignment) and optionally point to BPMN template/example. generate_uml (diagram_type bpmn) BPMN guide, uml://templates (bpmn), uml://examples (bpmn)
"Convert this class diagram into Mermaid code" Take PlantUML or description and output Mermaid classDiagram; optionally call generate_uml("mermaid", code). generate_uml uml://templates, uml://examples
"Explain quicksort with a diagram" Pick the right shape (flowchart, activity, state, or recursion tree), label each step with its Big-O complexity, and call generate_uml with the chosen diagram_type. generate_uml algorithm_explainer prompt, uml://recipes (algorithm_flowchart)
"Diagram the Transformer block from Vaswani+ 2017" Produce an architecture flowchart with citations in node labels and clickable arXiv links; call generate_uml with output_format svg to keep links clickable. generate_uml paper_concept_diagram prompt, uml://recipes (paper_concept)

Tools

  • generate_uml: Pass diagram_type (e.g. class, sequence, mermaid, bpmn) and code. Omit output_dir for URL / base64 only; set output_dir to save a file. generate_from_request in mcp_core/core/diagram_service.py calls generate_diagram in mcp_core/core/utils.py, then diagram_rendering.run_diagram_pipeline (Kroki first, optional fallbacks). Responses may include source (kroki, plantuml_server, or mermaid_ink).
  • validate_uml: Local validation of type, format, and light syntax before render (no network).

Resources

  • uml://types: Available diagram types and backends.
  • uml://templates: Starter template code per diagram type (including mermaid, mermaid_gantt-style content via Mermaid examples).
  • uml://examples: Full examples per diagram type.
  • uml://formats: Supported output formats per type.
  • uml://recipes: Named cross-type starter recipes (algorithm_flowchart, paper_concept) with the diagram_type and output_format to pass to generate_uml.
  • uml://server-info: Server name, version, tools, prompts.
  • uml://workflow: Recommended workflow: plan first (type, elements, relationships), then call generate_uml.

Prompts

Registered prompts that support the four scenarios above:

  • mermaid_sequence_api: Produce a Mermaid sequence diagram for an API call (client, API, auth/DB, request/response, optional alt); then call generate_uml("mermaid", code).
  • mermaid_gantt: Produce a Mermaid Gantt chart with title, dateFormat, sections, and tasks; then call generate_uml("mermaid", code).
  • bpmn_process_guide: Explain how to draw a BPMN process (elements, flow, BPMN 2.0.2); point to uml://templates / uml://examples (bpmn), the BPMN guide, and generate_uml("bpmn", ...).
  • convert_class_to_mermaid: Convert a class diagram (PlantUML or prose) into Mermaid classDiagram and optionally call generate_uml("mermaid", code).
  • algorithm_explainer: Pick the right shape for an algorithm (flowchart, activity, state, recursion tree), label every step with its Big-O complexity, and apply per-backend layout rules that minimise crossing arrows before calling generate_uml.
  • paper_concept_diagram: Visualise a concept from one or more academic papers; encode citations in node labels and add clickable arXiv/DOI links (Mermaid click, PlantUML [[ ]], D2 link:, Graphviz URL=). Recommends output_format svg so links stay clickable.

Other diagram prompts (e.g. class_diagram, sequence_diagram, uml_diagram_with_thinking) remain available for general UML generation.

Supported diagram types

The server supports (among others): class, sequence, activity, usecase, state, component, deployment, object, mermaid, d2, graphviz, erd, blockdiag, packetdiag, bpmn, c4plantuml. See uml://types for the full list and descriptions.

Reference

  • Kroki cheatsheet and docs for syntax and supported diagram types.
  • BPMN 2.0.2 (OMG) for BPMN terminology and element set.
  • Skill: .skill/skills/uml-diagramming/SKILL.md and references/DIAGRAM-TYPES.md for type mappings and examples.