Render D2 diagram source code to SVG or ASCII art using the D2 WASM engine.

D2 is a diagram scripting language. This tool compiles and renders D2 code without requiring the d2 binary — it uses the @terrastruct/d2 WASM package directly.

Args:

• d2_code (string): D2 source code to render

• theme_id (number): Theme ID (default: 0). See d2_list_themes for options. Key themes: 0=Neutral Default, 3=Flagship Terrastruct, 300=Terminal, 200=Dark Mauve

• dark_theme_id (number): Dark mode theme ID (optional)

• layout ('dagre' | 'elk'): Layout engine (default: 'dagre'). WARNING: elk is extremely slow in WASM — do NOT use unless explicitly requested. Dagre handles all diagram types well.

• sketch (boolean): Hand-drawn style (default: false)

• pad (number): Padding pixels (default: 100)

• center (boolean): Center in viewbox (default: false)

• scale (number): Scale factor, e.g. 0.5 halves size. Default fits SVG to screen. Set 1 to disable.

• animate_interval (number): Animate multi-board diagrams (layers/scenarios/steps) at this ms interval. Requires target to be set. E.g. animate_interval=1000, target='*'

• target (string): Which board to render. '*' = all boards (needs animate_interval > 0). 'layers.x' = specific layer. Default = root board only.

• ascii (boolean): Output ASCII art instead of SVG (default: false)

• ascii_mode ('standard' | 'extended'): ASCII char set. 'extended' uses Unicode (default).

• no_xml_tag (boolean): Omit declaration for direct HTML embedding (default: false)

• skip_fonts (boolean): Strip embedded font data from SVG (DEFAULT: true). Only set false if user explicitly requests embedded fonts.

Returns: SVG markup string (or ASCII art if ascii=true). SVG output starts with (unless no_xml_tag=true)

Examples:

• Simple: d2_code="a -> b: connects"

• Architecture: d2_code="server -> db: query\nserver -> cache: read"

• Styled: d2_code="x: { style.fill: '#4a90d9' }\nx -> y", theme_id=3

• ASCII preview: d2_code="a -> b -> c", ascii=true

• Animated steps: d2_code="steps: { s1: {a} s2: {a -> b} }", animate_interval=1000, target="*"

• With embedded fonts: skip_fonts=false (only when user explicitly requests it)

• HTML embed: no_xml_tag=true

Error Handling:

• Returns error with syntax details if D2 code is invalid

• Use d2_validate first to check syntax before rendering

Validate D2 diagram source code for syntax and semantic errors using the WASM engine.

Uses compile step to detect all errors without rendering. No d2 binary required.

Args:

• d2_code (string): D2 source code to validate

Returns: JSON object: { "valid": boolean, // Whether the code is syntactically and semantically valid "error": string // Error message if invalid (omitted if valid) }

Examples:

• Check before rendering: validate first, then d2_render only if valid=true

• Debug syntax: get specific line/column error info

Error Handling:

• Returns { valid: false, error: "..." } with specific error details

• Never throws — always returns a structured result

Parse and summarize the structure of D2 source code without rendering.

Returns a human-readable text summary of all shapes, containers, connections, and boards (layers/steps/scenarios) in the diagram. Uses the compile step only — no rendering occurs, so this is fast (~100ms) regardless of diagram complexity.

Use this INSTEAD of d2_render(ascii=true) for structural previews. The ASCII renderer has known bugs with cross-container connections and reverse edges. This tool produces reliable output for all diagram types.

Args:

• d2_code (string): D2 source code to inspect

Returns: Structured text summary, e.g.: Shapes (4): - cp [rectangle] "Control Plane" - cp.listener [rectangle] "API Gateway" - cp.grpc [rectangle] "gRPC Server" - agent [rectangle] "Data Plane Agent"

Connections (2):
  cp.grpc -> agent.stream : "mirror request"
  agent.stream -> cp.grpc : "response"

Works correctly for all diagram types:

• Architecture diagrams with nested containers and cross-container connections

• Sequence diagrams (filters out internal lifeline-end nodes)

• ER diagrams (sql_table shapes, FK connections shown at table level)

• UML class diagrams

• Layered/stepped/scenario diagrams (each board summarized)

• State machines, flowcharts, grid dashboards

Error handling:

• Returns compile errors if D2 code is invalid (same as d2_validate)

Format D2 diagram source code using the d2 binary formatter.

Normalizes whitespace, indentation, and syntax to D2's canonical style. The formatted output is semantically equivalent to the input.

NOTE: This tool requires the d2 binary to be installed (unlike d2_render and d2_validate which use WASM). Install from https://d2lang.com or set D2_PATH env var.

Args:

• d2_code (string): D2 source code to format

Returns: Formatted D2 source code string.

Examples:

• Clean up: format "a->b:label" to "a -> b: label"

• Normalize after editing: run on any hand-written D2 code

Error Handling:

• Returns error if d2 binary is not found (d2_render still works without it)

• Returns error if code has syntax errors (format requires valid syntax)

List all available D2 diagram themes with their IDs and names.

Use theme IDs with d2_render's theme_id parameter. No d2 binary required — theme list is built-in.

Args: (none)

Returns: JSON object: { "light": [{ "id": number, "name": string }], "dark": [{ "id": number, "name": string }] }

Notable themes:

• 0: Neutral Default (clean, professional — good default)

• 3: Flagship Terrastruct (vibrant, colorful)

• 8: Colorblind Clear (accessible palette)

• 200: Dark Mauve (dark mode)

• 300: Terminal (monospace, dot-fill containers, uppercase labels)

• 302: Origami (paper-like aesthetic)

• 303: C4 (C4 architecture diagram style)

List available D2 layout engines with descriptions and feature support.

Use layout names with d2_render's layout parameter. No d2 binary required — layout list is built-in.

Args: (none)

Returns: JSON object: { "layouts": [{ "name": string, "description": string, "features": string[] // Supported features }] }

Layout guidance:

• dagre: Default. Fast, good for most flowcharts and architecture diagrams.

• elk: Better for complex graphs, supports ancestor-to-descendant connections, width/height on containers. Slower than dagre.