Specky

Generate Mermaid Diagram

sdd_generate_diagram

Read-onlyIdempotent

Generate a Mermaid diagram from a specification artifact, with support for 17 diagram types spanning software engineering.

Instructions

Generates a single Mermaid diagram from a specification artifact. Supports 17 diagram types: flowchart, sequence, class, ER, state machine, C4 context, C4 container, C4 component, C4 code, activity, use case, DFD (data flow), deployment, network topology, Gantt, pie chart, and mind map.

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": {
      "diagram_type": "<diagram_type>",
      "source": "<source>"
    },
    "name": "sdd_generate_diagram"
  }
}

Input Schema

Name	Required	Description	Default
`source`	Yes	Which artifact to generate the diagram from.
`spec_dir`	No	Spec directory path (relative to workspace root)	.specs
`diagram_type`	Yes	Type of Mermaid diagram to generate. 17 types covering all software engineering diagram categories.
`feature_number`	No	Feature number (zero-padded, e.g. '001')	001

Schema Changelog

Changes observed during successful MCP inspections.

First observedv3.4.0-rc.14May 3, 2026

TDQS

B3.4/5.0

Behavior3/5

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

Annotations already convey read-only, non-destructive, idempotent behavior. The description does not contradict annotations but adds minimal behavioral context beyond what annotations provide. It does not disclose any side effects or additional constraints.

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

Conciseness4/5

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

Two sentences, front-loaded with action, no unnecessary words. However, could be slightly more concise by integrating diagram types list into sentence.

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?

With no output schema, the description could mention return value. It adequately covers purpose and diagram types but lacks guidance on usage and output. Adequate for a 4-parameter read-only tool.

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

Parameters3/5

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

Schema description coverage is 100%, so the schema itself documents parameters well. The description lists diagram types but adds no new semantic meaning beyond the schema. Baseline 3 is appropriate.

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 clearly states the tool generates a single Mermaid diagram from a specification artifact, and lists all 17 supported diagram types. It distinguishes from sibling tools like sdd_generate_all_diagrams which generates all diagrams.

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

Usage Guidelines2/5

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

No guidance on when to use this tool vs alternatives. There is no mention of when to use a single diagram vs generating all diagrams, or when to use different source artifacts. Missing context for appropriate usage.

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

Deploy Server