Excalidraw · Holon

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io.github.holon-sh/excalidrawv0.0.1 GitHub verified

A shared Excalidraw board that people and agents draw on together

Design & Creative

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Registry entry

Open in the registry

{
  "_meta": {
    "io.modelcontextprotocol.registry/official": {
      "status": "active",
      "isLatest": true,
      "updatedAt": "2026-11-15T01:27:06.82351Z",
      "publishedAt": "2026-11-15T01:27:06.82351Z",
      "statusChangedAt": "2026-11-15T01:27:06.82351Z"
    }
  },
  "server": {
    "name": "io.github.holon-sh/excalidraw",
    "_meta": {
      "io.modelcontextprotocol.registry/publisher-provided": {
        "sh.holon": {
          "egress": [
            {
              "host": "{S3_HOST}",
              "ports": [
                443
              ]
            }
          ]
        }
      }
    },
    "icons": [
      {
        "src": "https://excalidraw.holonlabs.io/favicon.svg",
        "sizes": [
          "any"
        ],
        "mimeType": "image/svg+xml"
      },
      {
        "src": "https://excalidraw.holonlabs.io/apple-touch-icon.png",
        "sizes": [
          "180x180"
        ],
        "mimeType": "image/png"
      }
    ],
    "title": "Excalidraw · Holon",
    "$schema": "https://static.modelcontextprotocol.io/schemas/2025-12-11/server.schema.json",
    "remotes": [
      {
        "url": "https://excalidraw.holonlabs.io/mcp/excalidraw",
        "type": "streamable-http"
      }
    ],
    "version": "0.0.1",
    "packages": [
      {
        "transport": {
          "url": "http://localhost:3000/mcp",
          "type": "streamable-http"
        },
        "identifier": "docker.io/holonlabs/excalidraw:0.0.1",
        "registryType": "oci",
        "environmentVariables": [
          {
            "name": "S3_HOST",
            "description": "Host of the S3-compatible API that keeps boards, such as <account id>.r2.cloudflarestorage.com. Without it, boards last as long as the server does."
          },
          {
            "name": "S3_BUCKET",
            "default": "excalidraw-boards",
            "description": "Bucket that keeps boards."
          },
          {
            "name": "S3_REGION",
            "default": "auto",
            "description": "Region requests are signed for: auto for R2, the bucket's own for providers with regions."
          },
          {
            "name": "S3_ACCESS_KEY_ID",
            "isSecret": true,
            "description": "Access key of a token that can read and write the bucket's objects."
          },
          {
            "name": "S3_SECRET_ACCESS_KEY",
            "isSecret": true,
            "description": "Secret of that token."
          }
        ]
      }
    ],
    "repository": {
      "url": "https://github.com/holon-sh/excalidraw",
      "source": "github"
    },
    "websiteUrl": "https://excalidraw.holonlabs.io",
    "description": "A shared Excalidraw board that people and agents draw on together"
  }
}

Maintain this server? Claim it

Try it

Call this server's tools from your browser. Nothing to install.

https://excalidraw.holonlabs.io/mcp/excalidraw

Requests go through mcptry because browsers can't call most MCP servers directly. Header values are sent to the server for that request only and are never stored or logged.

Tool list from our last check. Connect live to refresh it.

draw

Draw on a board: boxes (rectangle, ellipse, diamond), text, arrows between two shapes, and frames that hold shapes under a name. Everyone with the board open sees it at once. Give shapes your own short ids to join them with arrows and put them in frames in the same call. Leave out x and y, and the board lays new shapes out along their arrows, below what is already there. A box sizes itself to its text unless you give a width and height, and a frame wraps the shapes in it.

boardstring, required

The board's id, as in its URL.

shapesarray, required

directionstring

Which way arrows run between the shapes the board places: right unless given.

This tool isn't marked read-only, so it may change something on the server or in an account you connected.

I understand, run it anyway

Try it

Call this server's tools from your browser. Nothing to install.

https://excalidraw.holonlabs.io/mcp/excalidraw

Requests go through mcptry because browsers can't call most MCP servers directly. Header values are sent to the server for that request only and are never stored or logged.

Tool list from our last check. Connect live to refresh it.

draw

boardstring, required

The board's id, as in its URL.

shapesarray, required

directionstring

Which way arrows run between the shapes the board places: right unless given.

This tool isn't marked read-only, so it may change something on the server or in an account you connected.

I understand, run it anyway

Tools (6)

draw

Argument	Type	Description
board*	string	The board's id, as in its URL.
shapes*	array
direction	string	Which way arrows run between the shapes the board places: right unless given.

Input schema (JSON)

{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "board",
    "shapes"
  ],
  "properties": {
    "board": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{1,64}$",
      "description": "The board's id, as in its URL."
    },
    "shapes": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "x": {
            "type": "number",
            "description": "Left edge, in pixels. Leave out x and y of a new shape to have the board place it."
          },
          "y": {
            "type": "number",
            "description": "Top edge, in pixels. y grows downward."
          },
          "id": {
            "type": "string",
            "maxLength": 64,
            "minLength": 1,
            "description": "Names the shape. The id of a shape on the board changes that shape, keeping the fields you leave out."
          },
          "to": {
            "type": "string",
            "description": "The id of the shape an arrow points at."
          },
          "fill": {
            "type": "string",
            "description": "A box's background, as a CSS color."
          },
          "from": {
            "type": "string",
            "description": "The id of the shape an arrow leaves."
          },
          "text": {
            "type": "string",
            "maxLength": 2000,
            "description": "The label of a box or an arrow, what a text shape says, or a frame's name."
          },
          "type": {
            "enum": [
              "rectangle",
              "ellipse",
              "diamond",
              "text",
              "arrow",
              "frame"
            ],
            "type": "string",
            "description": "Required for a new shape."
          },
          "color": {
            "type": "string",
            "description": "Stroke color, as a CSS color."
          },
          "frame": {
            "type": "string",
            "description": "The id of the frame the shape sits in. An empty string takes it out."
          },
          "width": {
            "type": "number",
            "exclusiveMinimum": 0
          },
          "height": {
            "type": "number",
            "exclusiveMinimum": 0
          },
          "stroke": {
            "enum": [
              "solid",
              "dashed",
              "dotted"
            ],
            "type": "string",
            "description": "The line of a box's outline or an arrow."
          },
          "fontSize": {
            "type": "number",
            "maximum": 200,
            "minimum": 8,
            "description": "The text's size in pixels: 20 unless given, 28 or 36 for a heading."
          }
        },
        "additionalProperties": false
      },
      "maxItems": 500,
      "minItems": 1
    },
    "direction": {
      "enum": [
        "right",
        "down"
      ],
      "type": "string",
      "description": "Which way arrows run between the shapes the board places: right unless given."
    }
  },
  "additionalProperties": false
}

erase

Erase shapes from a board by id. An arrow attached to an erased shape stays, so erase it too if it should go. The shapes in an erased frame stay.

Argument	Type	Description
ids*	array
board*	string	The board's id, as in its URL.

Input schema (JSON)

{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "board",
    "ids"
  ],
  "properties": {
    "ids": {
      "type": "array",
      "items": {
        "type": "string"
      },
      "maxItems": 500,
      "minItems": 1
    },
    "board": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{1,64}$",
      "description": "The board's id, as in its URL."
    }
  },
  "additionalProperties": false
}

get_image

For the board's page: read the file of an image on the board, as a data URL. Without one, the board has no such file.

read-only

Argument	Type	Description
id*	string	The fileId of the image's Excalidraw element.
board*	string	The board's id, as in its URL.

Input schema (JSON)

{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "board",
    "id"
  ],
  "properties": {
    "id": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{1,64}$",
      "description": "The fileId of the image's Excalidraw element."
    },
    "board": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{1,64}$",
      "description": "The board's id, as in its URL."
    }
  },
  "additionalProperties": false
}

put_image

For the board's page: store the file of an image on the board, as a data URL.

Argument	Type	Description
id*	string	The fileId of the image's Excalidraw element.
board*	string	The board's id, as in its URL.
dataURL*	string

Input schema (JSON)

{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "board",
    "id",
    "dataURL"
  ],
  "properties": {
    "id": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{1,64}$",
      "description": "The fileId of the image's Excalidraw element."
    },
    "board": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{1,64}$",
      "description": "The board's id, as in its URL."
    },
    "dataURL": {
      "type": "string",
      "pattern": "^data:image\\/[a-z0-9.+-]+;base64,[A-Za-z0-9+/]+=*$",
      "maxLength": 2000000
    }
  },
  "additionalProperties": false
}

read_board

Read a shared Excalidraw board and open it. Returns its shapes and the URL where anyone can watch and edit it live. Leave out board to start a new one.

read-only

Argument	Type	Description
board	string	The board's id, as in its URL.

Input schema (JSON)

{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "properties": {
    "board": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{1,64}$",
      "description": "The board's id, as in its URL."
    }
  },
  "additionalProperties": false
}

sync

For the board's page: send the Excalidraw elements it changed and where its pointer is. With since, also receive the elements changed elsewhere and everyone else's cursors.

Argument	Type	Description
board*	string	The board's id, as in its URL.
since	integer
client*	string	Names the calling page, so that it is not told its own changes.
elements*	array
presence	object

Input schema (JSON)

{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "board",
    "client",
    "elements"
  ],
  "properties": {
    "board": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{1,64}$",
      "description": "The board's id, as in its URL."
    },
    "since": {
      "type": "integer",
      "maximum": 9007199254740991,
      "minimum": 0
    },
    "client": {
      "type": "string",
      "maxLength": 64,
      "minLength": 1,
      "description": "Names the calling page, so that it is not told its own changes."
    },
    "elements": {
      "type": "array",
      "items": {
        "type": "object",
        "required": [
          "id",
          "version",
          "versionNonce",
          "isDeleted"
        ],
        "properties": {
          "id": {
            "type": "string",
            "maxLength": 64,
            "minLength": 1
          },
          "updated": {
            "type": "number"
          },
          "version": {
            "type": "integer",
            "maximum": 9007199254740991,
            "minimum": 0
          },
          "isDeleted": {
            "type": "boolean"
          },
          "versionNonce": {
            "type": "integer",
            "maximum": 9007199254740991,
            "minimum": -9007199254740991
          }
        },
        "additionalProperties": {}
      },
      "maxItems": 5000
    },
    "presence": {
      "type": "object",
      "required": [
        "name",
        "x",
        "y",
        "selected"
      ],
      "properties": {
        "x": {
          "type": "number"
        },
        "y": {
          "type": "number"
        },
        "name": {
          "type": "string",
          "maxLength": 40,
          "minLength": 1
        },
        "selected": {
          "type": "array",
          "items": {
            "type": "string",
            "maxLength": 64
          },
          "maxItems": 200
        }
      },
      "additionalProperties": false
    }
  },
  "additionalProperties": false
}

Excalidraw · Holon

Registry entry

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draw

Excalidraw · Holon

Registry entry

Try it

draw

Install

Tools (6)

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