Excalidraw Diagram Generator (MCP Edition)

Create diagrams on a live Excalidraw canvas using MCP tools. The canvas runs in a browser and updates in real time.

Mental Model

You are placing shapes on a 2D canvas and drawing arrows between them.

(0,0) ────────── x increases ──────────► │ │ ┌──────────┐ ┌──────────┐ │ │ Box A │─────►│ Box B │ │ └──────────┘ └──────────┘ │ │ y ▼ increases ┌──────────┐ │ │ Box C │ ▼ └──────────┘

Everything is (x, y, width, height). That's it.

The 5 Tools You Actually Need

Tool What It Does When to Use

read_diagram_guide

Returns color palette + sizing rules First call. Read once, use throughout.

batch_create_elements

Create many shapes + arrows at once Main workhorse. Create your whole diagram in 1-2 calls.

get_canvas_screenshot

Take a photo of the current canvas After every batch. Verify it looks right.

clear_canvas

Wipe everything Start fresh before a new diagram.

export_to_image

Save as PNG or SVG Final step if user wants an image file.

Other useful tools: describe_scene (text description of canvas), create_from_mermaid (quick diagram from Mermaid syntax), export_scene (save as .excalidraw JSON file), set_viewport (zoom/pan to fit), export_to_excalidraw_url (shareable link).

How Shapes Work

A shape has: type, position (x, y), size (width, height), colors, and label text.

{ "type": "rectangle", "id": "my-box", "x": 100, "y": 100, "width": 180, "height": 70, "backgroundColor": "#a5d8ff", "strokeColor": "#1971c2", "roughness": 0, "text": "My Service\nPort 8080" }

Key points:

• text puts a label directly inside the shape (MCP handles the binding for you)

• roughness: 0 = clean lines. roughness: 1 = hand-drawn look.

• Use \n for multi-line labels

• Shapes: rectangle , ellipse , diamond , text (standalone)

How Arrows Work

Arrows connect shapes by ID. The MCP server auto-routes them to shape edges.

{ "type": "arrow", "x": 0, "y": 0, "startElementId": "my-box", "endElementId": "other-box", "strokeColor": "#1971c2", "text": "HTTP" }

Key points:

• startElementId / endElementId = the id of the shape to connect to

• The arrow auto-routes to the nearest edges. You do NOT calculate edge points.

• x, y are still required but can be approximate — binding overrides them

• text adds a label on the arrow

• strokeStyle: "dashed" = async/optional flows. "dotted" = weak dependency.

• startArrowhead / endArrowhead = "arrow" , "dot" , "triangle" , "bar" , or null

Step-by-Step Workflow

Step 1: Understand What to Draw

Read the codebase. Identify:

• Components (services, databases, APIs, queues, frontends)

• Connections (which components talk to which, and how)

• Layers (group related components into rows or zones)

When a sample diagram is provided (ASCII art, text mockup, screenshot, etc.):

• Preserve ALL text and detail from the sample by default. Do not simplify, summarize, or omit labels, annotations, bullet points, or sublabels present in the sample.

• Extract every node's full text (titles, subtitles, tool names, metrics, details) and reproduce it verbatim in shape labels using \n for multiline.

• Preserve section headers, status annotations (e.g. "Fail = Stop & Notify"), and arrow labels exactly as written.

• Size boxes large enough to fit the full text (increase height/width beyond defaults as needed).

• The sample is the source of truth for content — you may improve layout, colors, and styling, but never drop information.

Step 2: Read the Design Guide

mcp__excalidraw__read_diagram_guide()

This returns the color palette, sizing rules, and layout best practices. Use it.

Step 3: Clear and VERIFY the Canvas

mcp__excalidraw__clear_canvas() mcp__excalidraw__get_canvas_screenshot() // MUST verify empty!

Critical: Previous diagrams can leave ghost elements. Always screenshot after clearing to confirm the canvas is truly empty before creating new elements. If elements remain, clear again.

Step 4: Plan Your Layout on Paper

Before calling any create tool, sketch the layout mentally:

Vertical flow (most common): Row 1 (y=0): Zone backgrounds (large dashed rectangles) Row 2 (y=60): Entry points / Users Row 3 (y=350): Middle layer (APIs, services) Row 4 (y=650): Data layer (databases, storage)

Columns: x = 40, 440, 840 (spaced 400px apart for labeled arrows) Box size: 230 x 160 (standard) | 200 x 120 (for decision diamonds) Spacing between rows: ~200px gap after accounting for box height Spacing between boxes in a row: 180px gap (for arrow labels)

Step 5: Create Everything in One Batch

Call batch_create_elements with ALL elements at once. This ensures arrow bindings resolve correctly (arrows can reference shape IDs created in the same batch).

Order of elements in the array:

• Zone backgrounds (large dashed rectangles) — so they render behind everything

• Shapes (rectangles, ellipses, diamonds) — with id set for arrow references

• Arrows — using startElementId / endElementId

• Standalone text labels (titles, annotations)

Step 6: Screenshot and Verify

mcp__excalidraw__get_canvas_screenshot()

Look at the image. Check:

• Are all labels readable?

• Are arrows connecting the right shapes?

• Is spacing even?

• Are zones encompassing their children?

Step 7: Fix and Adjust

Use update_element to tweak positions, colors, or text. Use delete_element

• create_element for bigger changes. Then screenshot again.

Step 8: Zoom to Fit

mcp__excalidraw__set_viewport({ scrollToContent: true })

Step 9: Export (if requested)

mcp__excalidraw__export_to_image({ format: "png", filePath: "/path/to/output.png" }) mcp__excalidraw__export_scene({ filePath: "/path/to/output.excalidraw" }) mcp__excalidraw__export_to_excalidraw_url() // shareable link

Complete Example: 3-Layer Architecture

This shows exactly what to pass to batch_create_elements :

{ "elements": [ // --- ZONE BACKGROUNDS (render behind everything) --- { "type": "rectangle", "id": "zone-frontend", "x": 0, "y": 0, "width": 500, "height": 160, "backgroundColor": "#e9ecef", "strokeColor": "#868e96", "strokeStyle": "dashed", "opacity": 40, "roughness": 0 }, { "type": "text", "x": 10, "y": 10, "text": "Frontend Layer", "fontSize": 14, "strokeColor": "#868e96" }, { "type": "rectangle", "id": "zone-backend", "x": 0, "y": 200, "width": 500, "height": 160, "backgroundColor": "#eebefa", "strokeColor": "#9c36b5", "strokeStyle": "dashed", "opacity": 30, "roughness": 0 }, { "type": "text", "x": 10, "y": 210, "text": "Backend Layer", "fontSize": 14, "strokeColor": "#9c36b5" },

// --- SHAPES (give each an id so arrows can reference them) ---
{
  "type": "rectangle", "id": "react-app",
  "x": 40, "y": 50, "width": 180, "height": 70,
  "backgroundColor": "#a5d8ff", "strokeColor": "#1971c2", "roughness": 0,
  "text": "React App\nFrontend"
},
{
  "type": "rectangle", "id": "api-server",
  "x": 40, "y": 250, "width": 180, "height": 70,
  "backgroundColor": "#d0bfff", "strokeColor": "#7048e8", "roughness": 0,
  "text": "API Server\nExpress.js"
},
{
  "type": "rectangle", "id": "database",
  "x": 280, "y": 250, "width": 180, "height": 70,
  "backgroundColor": "#b2f2bb", "strokeColor": "#2f9e44", "roughness": 0,
  "text": "PostgreSQL\nDatabase"
},

// --- ARROWS (connect shapes by ID) ---
{
  "type": "arrow", "x": 130, "y": 120,
  "startElementId": "react-app", "endElementId": "api-server",
  "strokeColor": "#1971c2", "text": "REST API"
},
{
  "type": "arrow", "x": 220, "y": 285,
  "startElementId": "api-server", "endElementId": "database",
  "strokeColor": "#2f9e44", "text": "SQL"
},

// --- TITLE ---
{
  "type": "text", "x": 100, "y": -40,
  "text": "System Architecture", "fontSize": 24, "strokeColor": "#1e1e1e"
}

] }

Complete Example: Data Flow Diagram (Parameter Threading)

Shows a parameter traced through 5 layers with split/converge paths, decision node, and side annotations:

{ "elements": [ // --- TITLE --- {"type": "text", "x": 20, "y": 10, "text": "Data Flow: parameter_name Threading", "fontSize": 24, "strokeColor": "#1e1e1e"}, {"type": "text", "x": 20, "y": 48, "text": "Subtitle describing the trace", "fontSize": 16, "strokeColor": "#868e96"},

// --- WHY SECTION (top-right, first-principles context) ---
{"type": "rectangle", "id": "why-bg", "x": 460, "y": 80, "width": 440, "height": 310,
 "backgroundColor": "#e9ecef", "strokeColor": "#868e96", "roughness": 0},
{"type": "text", "x": 480, "y": 95, "text": "WHY: The Problem", "fontSize": 20, "strokeColor": "#e03131"},
{"type": "text", "x": 480, "y": 135, "text": "1. What currently happens", "fontSize": 16, "strokeColor": "#1e1e1e"},
{"type": "text", "x": 480, "y": 195, "text": "2. Why it's expensive/wrong", "fontSize": 16, "strokeColor": "#e03131"},
{"type": "text", "x": 480, "y": 275, "text": "3. Gap in current design", "fontSize": 16, "strokeColor": "#1e1e1e"},
{"type": "text", "x": 480, "y": 335, "text": "Solution: what this change does", "fontSize": 16, "strokeColor": "#2f9e44"},

// --- FLOW BOXES (center column, 150px vertical pitch) ---
{"type": "rectangle", "id": "l1", "x": 60, "y": 420, "width": 300, "height": 65,
 "backgroundColor": "#a5d8ff", "strokeColor": "#1971c2", "roughness": 0,
 "text": "Entry Point\nfile/path.py"},

// Split into two paths
{"type": "rectangle", "id": "l2a", "x": -100, "y": 570, "width": 290, "height": 65,
 "backgroundColor": "#a5d8ff", "strokeColor": "#1971c2", "roughness": 0,
 "text": "Path A\nfile/path_a.py"},
{"type": "rectangle", "id": "l2b", "x": 230, "y": 570, "width": 290, "height": 65,
 "backgroundColor": "#a5d8ff", "strokeColor": "#1971c2", "roughness": 0,
 "text": "Path B\nfile/path_b.py"},

// Converge point
{"type": "rectangle", "id": "l4", "x": 60, "y": 720, "width": 300, "height": 65,
 "backgroundColor": "#eebefa", "strokeColor": "#9c36b5", "roughness": 0,
 "text": "Convergence Point\nfile/path_merge.py"},

// Decision
{"type": "diamond", "id": "dec", "x": 110, "y": 870, "width": 200, "height": 120,
 "backgroundColor": "#fff3bf", "strokeColor": "#fab005", "roughness": 0,
 "text": "condition?"},

// Outcome branches
{"type": "rectangle", "id": "yes", "x": -100, "y": 1080, "width": 260, "height": 65,
 "backgroundColor": "#ffc9c9", "strokeColor": "#e03131", "roughness": 0,
 "text": "Expensive Operation"},
{"type": "rectangle", "id": "no", "x": 250, "y": 1080, "width": 220, "height": 65,
 "backgroundColor": "#b2f2bb", "strokeColor": "#2f9e44", "roughness": 0,
 "text": "Skip / Fast Path"},

// --- ARROWS (bound by ID, auto-routed) ---
{"type": "arrow", "x": 150, "y": 485, "startElementId": "l1", "endElementId": "l2a",
 "text": "Path A label", "strokeColor": "#1971c2"},
{"type": "arrow", "x": 280, "y": 485, "startElementId": "l1", "endElementId": "l2b",
 "text": "Path B label", "strokeColor": "#1971c2"},
{"type": "arrow", "x": 45, "y": 635, "startElementId": "l2a", "endElementId": "l4",
 "text": "data form", "strokeColor": "#9c36b5"},
{"type": "arrow", "x": 375, "y": 635, "startElementId": "l2b", "endElementId": "l4",
 "text": "data form", "strokeColor": "#1971c2", "strokeStyle": "dashed"},
{"type": "arrow", "x": 210, "y": 785, "startElementId": "l4", "endElementId": "dec",
 "strokeColor": "#2f9e44"},
{"type": "arrow", "x": 150, "y": 990, "startElementId": "dec", "endElementId": "yes",
 "text": "True", "strokeColor": "#e03131"},
{"type": "arrow", "x": 270, "y": 990, "startElementId": "dec", "endElementId": "no",
 "text": "False", "strokeColor": "#2f9e44"},

// --- LAYER LABELS (left column, gray) ---
{"type": "text", "x": -100, "y": 420, "text": "Layer 1\nEntry", "fontSize": 14, "strokeColor": "#868e96"},
{"type": "text", "x": -210, "y": 570, "text": "Layer 2\nBackend", "fontSize": 14, "strokeColor": "#868e96"},

// --- DATA FORM ANNOTATIONS (right column, orange) ---
{"type": "text", "x": 570, "y": 440, "text": "Data form: Python bool", "fontSize": 14, "strokeColor": "#e8590c"},
{"type": "text", "x": 570, "y": 590, "text": "Data form: JSON / arg", "fontSize": 14, "strokeColor": "#e8590c"},
{"type": "text", "x": 570, "y": 740, "text": "Data form: Dataclass", "fontSize": 14, "strokeColor": "#e8590c"}

] }

Color Palette (Quick Reference)

Component Type Background Stroke When to Use

Frontend/UI #a5d8ff

#1971c2

React, Next.js, web apps

Backend/API #d0bfff

#7048e8

API servers, processors

Database #b2f2bb

#2f9e44

PostgreSQL, Redis, MongoDB

Storage #ffec99

#f08c00

S3, file systems

AI/ML #e599f7

#9c36b5

ML models, AI services

External API #ffc9c9

#e03131

Third-party services

Queue/Event #fff3bf

#fab005

Kafka, RabbitMQ, SQS

Cache #ffe8cc

#fd7e14

Redis cache, Memcached

Decision/Gate #ffd8a8

#e8590c

Conditionals, routers

Zone/Group #e9ecef

#868e96

Logical groupings

Rule: Same-role shapes get same colors. Limit to 3-4 fill colors per diagram.

Sizing Rules

Err on the side of too much space. Tight spacing is the #1 mistake — arrows and their labels get hidden when boxes are too close. When in doubt, double the gap you think you need. Diagrams that feel "too spread out" in your head almost always look right on screen.

CRITICAL: Arrow labels need ~120px of clear space between boxes to be visible. If an arrow has a text label (e.g. "auto deploy", "All pass"), the gap between the two connected boxes MUST be at least 150px. Arrows without labels still need 100px minimum.

Property Value Why

Box width 200-240px Fits multiline labels with breathing room

Box height 120-160px Fits 3-4 line labels comfortably

Horizontal gap (labeled arrows) 150-200px Arrow labels are ~80-120px wide, need clearance on both sides

Horizontal gap (unlabeled arrows) 100-120px Just the arrow line + breathing room

Column spacing (labeled) 400px 220px box + 180px gap

Column spacing (unlabeled) 340px 220px box + 120px gap

Row spacing 280-350px 150px box + 150px gap for arrows + annotations

Font size (labels) 16px Default, readable

Font size (titles) 20-24px Stands out as header

Font size (zone labels) 14px Subtle, doesn't compete

Zone opacity 25-40 Background, not foreground

Zone padding 50-60px around children Zone borders must NOT hug inner boxes

Section header to box gap 40px Headers need clearance from boxes below

Zone sizing rule: Calculate zone dimensions as: leftmost child x - 50 to rightmost child x + child width + 60 (horizontal), topmost child y - 55 to bottommost child y + child height + 60 (vertical). Always verify the zone fully wraps ALL children with visible padding on every side.

Arrow visibility test: Before finalizing, mentally check every labeled arrow — if the label text is longer than half the gap between boxes, increase the gap. Common offenders: "auto deploy", "rollback on failure", "All pass" — these labels are 80-150px wide and get clipped when gaps are <150px.

Layout Patterns

Vertical Flow (default for most diagrams)

Title (y = -40)

[Zone 1: y=0, height=260] [Box A: x=40] [Box B: x=440] [Box C: x=840]

[Zone 2: y=350, height=260] [Box D: x=40] [Box E: x=440]

[Zone 3: y=700, height=260] [Box F: x=240]

Arrows flow top to bottom. Cross-layer arrows use dashed style.

Horizontal Pipeline

[Source] ──► [Transform 1] ──► [Transform 2] ──► [Output] x=40 x=440 x=840 x=1240

All at same y . Arrows flow left to right. Use 400px column spacing for labeled arrows, 340px for unlabeled.

Hub and Spoke

     [Consumer A]
          ▲
          │

[Producer] ──► [Event Bus] ──► [Consumer B] │ ▼ [Consumer C]

Central shape at (300, 300). Spokes at ~200px radius.

Data Flow Diagram (parameter threading, call chains)

Best for: tracing a parameter/request through architectural layers, showing data transformations at each boundary.

Layer Labels Main Flow Column Side Annotations (left, gray) (center, colored) (right, orange)

Layer 1 ┌─────────────────────┐ Data form: Python bool User API │ Entry Point │ │ file/path.py │ └──────┬──────┬───────┘ │ │ ┌───────┘ └────────┐ ▼ ▼ Layer 2 ┌──────────┐ ┌──────────┐ Data form: JSON / bool Backend │ Path A │ │ Path B │ └────┬─────┘ └────┬─────┘ │ │ (dashed = direct) ▼ │ Layer 3 ┌──────────┐ │ Data form: Dataclass HTTP │ Server │ │ └────┬─────┘ │ └──────┬───────┘ (converge) ▼ Layer 4 ┌─────────────────────┐ Data form: IPC message Manager │ Manager │ └──────┬──────────────┘ ▼ Layer 5 ┌─────────────────────┐ Data form: Conditional Executor │ Executor │ └──────┬──────────────┘ ▼ ◇ Decision? ◇ /
True/ \False ▼ ▼ [Yes] [No]

Golden coordinates (validated):

Element x y width height

Main boxes 60 +150 per row 300 65

Split left -100 row_y 290 65

Split right 230 row_y 290 65

Decision diamond 110 row_y 200 120

Layer labels -100 to -50 aligned to box — fontSize: 14

Annotations 570 aligned to box — fontSize: 14

WHY section 460, y=80 — 440 310

Three-column structure:

• Left column (x < 0): Layer numbers + names in gray (#868e96 , fontSize 14)

• Center column (x: 60–360): Flow boxes with ComponentName\nfile/path.py

• Right column (x: 570): Data form annotations in orange (#e8590c , fontSize 14)

Color by layer role:

• Blue (#a5d8ff /#1971c2 ): User-facing API layers

• Purple (#eebefa /#9c36b5 ): Internal processing layers

• Green (#b2f2bb /#2f9e44 ): Execution layer + "skip/success" outcomes

• Yellow (#fff3bf /#fab005 ): Decision nodes

• Red (#ffc9c9 /#e03131 ): Expensive/dangerous operations

• Gray (#e9ecef /#868e96 ): Annotations, zones

Split and converge pattern:

• Split: Two arrows from one box, angled down-left and down-right

• Direct skip: Use strokeStyle: "dashed" for paths that skip layers

• Converge: Two arrows from different paths into one box below

"WHY" annotation box (first-principles context): Place a gray-background rectangle (top-right, x: 460 ) with 3-4 text items explaining the motivation. Use red stroke for the problem, green stroke for the solution.

Common Mistakes and Fixes

Mistake Fix

Ghost elements from previous diagram Always get_canvas_screenshot() after clear_canvas() . If old elements visible, clear again

Arrows don't connect Set startElementId /endElementId to valid shape id values

Shapes overlap Increase spacing. Use 240px column gap, 140px row gap

Labels cut off Make boxes wider (200px+) or use shorter text

Can't tell layers apart Add zone background rectangles with dashed stroke + low opacity

Too many colors Limit to 3-4 fill colors. Same role = same color

Diagram too cluttered Split into multiple diagrams, or use create_from_mermaid for quick drafts

Arrows cross messily Rearrange shapes so related ones are adjacent. Vertical flow reduces crossings

Annotations overlap with flow Use 3-column layout: labels (x<0), flow (x:60-360), annotations (x:570+)

Lost detail from sample diagram Sample is source of truth for content. Reproduce ALL text verbatim — titles, subtitles, tool lists, metrics, annotations. Size boxes larger if needed

Quick Start Templates

"Draw me a diagram of X"

1. Read the code to understand components and connections

2. Read the design guide

mcp__excalidraw__read_diagram_guide()

3. Clear canvas

mcp__excalidraw__clear_canvas()

4. Create everything in one batch

mcp__excalidraw__batch_create_elements(elements=[...])

5. Zoom to fit

mcp__excalidraw__set_viewport(scrollToContent=True)

6. Screenshot to verify

mcp__excalidraw__get_canvas_screenshot()

7. Adjust if needed, then export

"Quick diagram from description"

For simple diagrams, Mermaid is fastest:

mcp__excalidraw__create_from_mermaid( mermaidDiagram="graph TD; A[Frontend] -->|REST| B[API]; B -->|SQL| C[Database]" )

Export Options

Method Output Use Case

export_to_image(format="png")

PNG file Embed in docs, Slack, PRs

export_to_image(format="svg")

SVG file Scalable, embed in web pages

export_scene(filePath="...")

.excalidraw JSON Editable in excalidraw.com or VS Code

export_to_excalidraw_url()

Shareable URL Share with anyone, no file needed