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dgmo-mcp

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render_diagram

Read-onlyIdempotent

Convert DGMO markup into SVG or PNG for flowcharts, sequence, ER, and other diagrams. Returns SVG text or base64 PNG with a temp file path.

Instructions

Render DGMO markup to SVG or PNG. Returns SVG text or base64 PNG image. When format is "png", also saves the image to a temp file and returns the path. For DGMO syntax call get_language_reference.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
dgmoYesDGMO diagram markup. For syntax call get_language_reference.
themeNoColor themelight
widthNoCanvas width in px. Omit to let the diagram size itself from its content. Honoured exactly by the chart types that lay their content out into the canvas (bar, line, pie and the other data charts). A chart that sizes itself from its own nodes — org, sitemap, class, er, infra and the rest of the structured family — cannot go below its content and will return a wider canvas than asked for.
formatNoOutput formatsvg
heightNoCanvas height in px. Most chart types derive height from their content and ignore this; the data charts honour it.
paletteNoColor palette (slate, atlas, blueprint, tidewater, nord, catppuccin, tokyo-night)slate

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.29.5
    • changedInput schema / properties / dgmo / description
      Previous value: -"DGMO diagram markup. Color a label by appending a lowercase color name as the trailing token (e.g. \"Sales red\"); capitalize (\"Red\") to use a color word as literal text."New value: +"DGMO diagram markup. For syntax call get_language_reference."
  2. Changed2 schema fields changedv0.29.1
    • addedInput schema / properties / height
      Added value: +{
+  "description": "Canvas height in px. Most chart types derive height from their content and ignore this; the data charts honour it.",
+  "exclusiveMinimum": 0,
+  "type": "integer"
+}
    • addedInput schema / properties / width
      Added value: +{
+  "description": "Canvas width in px. Omit to let the diagram size itself from its content. Honoured exactly by the chart types that lay their content out into the canvas (bar, line, pie and the other data charts). A chart that sizes itself from its own nodes — org, sitemap, class, er, infra and the rest of the structured family — cannot go below its content and will return a wider canvas than asked for.",
+  "exclusiveMinimum": 0,
+  "type": "integer"
+}
  3. Addedv0.17.0
  4. Removedv0.12.0
  5. Changed2 schema fields changedv0.2.4
    • changedInput schema / properties / palette / default
      Previous value: -"nord"New value: +"slate"
    • changedInput schema / properties / palette / description
      Previous value: -"Color palette (nord, atlas, blueprint, slate, tidewater, solarized, catppuccin, rose-pine, gruvbox, tokyo-night, one-dark, dracula, monokai)"New value: +"Color palette (slate, atlas, blueprint, tidewater, nord, catppuccin, tokyo-night)"
  6. Addedv0.2.2
  7. Removedv0.1.21
  8. First observedv0.1.13

TDQS

A3.7/5.0
Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the return shape (SVG text vs base64 PNG) and the side effect that PNG format writes a temp file and returns its path. It still doesn't mention failure behavior for invalid markup.

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?

Three short sentences, front-loaded with the primary action and output formats, with no filler. The final syntax-pointer sentence is somewhat redundant with the schema's own note but still earns its place as a routing hint.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description correctly shoulders the return-value burden (SVG text or base64 PNG, plus temp file path). Given six parameters and a rendering operation, the main remaining gap is error/validation behavior, which is minor for a read-only render 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%, including detailed notes on width/height sizing and palette options, so the schema carries the parameter burden. The description only marginally extends this by tying the 'png' format value to the temp-file side effect. Baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (Render) and resource (DGMO markup) plus the output formats (SVG or PNG), so an agent knows exactly what the tool produces. It does not, however, differentiate itself from close siblings like preview_diagram or validate_diagram, which an agent might reasonably confuse it with.

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

Usage Guidelines3/5

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

The only routing guidance is 'For DGMO syntax call get_language_reference', which points to a dependency rather than explaining when to pick this tool over preview_diagram or validate_diagram. Usage context is implied by the name but never stated.

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

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