MCP prompts¶

Prompts are named text templates an MCP client can fetch with prompts/get and pass into the model context. UML-MCP registers 13 prompts across UML, Mermaid, BPMN, C4, and hardware/wiring categories. Source of truth: mcp_core/prompts/diagram_prompts.py.

Calling a prompt¶

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "prompts/get",
  "params": {
    "name": "uml_diagram_with_thinking",
    "arguments": { "diagram_type": "sequence" }
  }
}

Most prompts accept an optional context dict. The most common key is diagram_type, which selects the diagram type for the prompt.

General UML¶

Prompt	Purpose
`uml_diagram`	Base prompt: read `uml://types` and `uml://formats`, plan, then call `generate_uml` with raw source.
`uml_diagram_with_thinking`	Same workflow with explicit planning step ("Before writing code, briefly plan…"). Use this for complex diagrams.

Per-type UML¶

Prompt	Output
`class_diagram`	PlantUML class diagram from natural-language description; visibility, inheritance, composition, associations.
`sequence_diagram`	PlantUML sequence diagram with participants, lifelines, messages, activations.
`activity_diagram`	PlantUML activity diagram with start/end, decisions, forks, joins, swimlanes.
`usecase_diagram`	PlantUML use case diagram with actors, system boundary, include/extend.

Mermaid¶

Prompt	Output
`mermaid_sequence_api`	Mermaid `sequenceDiagram` for an API call (client, API, optional Auth/DB, request/response, optional `alt` blocks).
`mermaid_gantt`	Mermaid `gantt` chart with title, `dateFormat`, sections, dependencies (`after`), durations.
`convert_class_to_mermaid`	Convert a PlantUML class diagram (or prose description) into Mermaid `classDiagram`.

Live Mermaid examples

BPMN¶

Prompt	Output
`bpmn_process_guide`	Explains how to draw a BPMN process model (BPMN 2.0.2-aligned), pairs with `uml://templates` / `uml://examples` (key bpmn) and the BPMN guide.
`bpmn_executable_process`	Produces minimal executable BPMN 2.0 XML: start, tasks, gateways, end, sequenceFlow.

BPMN guide

BPMN prompts and SVG

Architecture¶

Prompt	Output
`c4_model`	C4 diagrams using PlantUML C4 includes: context or container views with relationships.

Hardware / wiring¶

Prompt	Output
`wireviz_harness`	WireViz YAML for cable/connector harnesses: connectors, cables, colors, pins.

Choosing the right prompt¶

flowchart TD
    Start([User intent]) --> Q1{Plan-then-generate?}
    Q1 -- yes --> Plan[uml_diagram_with_thinking]
    Q1 -- no  --> Q2{Diagram family?}
    Q2 -->|UML class/sequence/activity/usecase| UMLp[Per-type UML prompt]
    Q2 -->|Mermaid sequence or Gantt| MMp[mermaid_sequence_api / mermaid_gantt]
    Q2 -->|BPMN process| BPMNp[bpmn_process_guide / bpmn_executable_process]
    Q2 -->|Architecture| C4p[c4_model]
    Q2 -->|Cable harness| WVp[wireviz_harness]
    Q2 -->|Convert class -> mermaid| Convp[convert_class_to_mermaid]

Prompt + tool together

All prompts end by instructing the model to call generate_uml with the right diagram_type. Combined with the uml://workflow resource, you get plan → code → render in a single MCP turn.