Excalidraw MCP Server

Instructions

Implementation Reference

• src/index.js:442-478 (handler)

  The handler function for the 'get_resource' tool. It validates input using ResourceSchema, switches on the resource type (scene, library, theme, elements), retrieves data from in-memory state, and returns JSON-formatted content.

  case 'get_resource': {
    const params = ResourceSchema.parse(args);
    const { resource } = params;
    logger.info('Getting resource', { resource });
    
    let result;
    switch (resource) {
      case 'scene':
        result = {
          theme: sceneState.theme,
          viewport: sceneState.viewport,
          selectedElements: Array.from(sceneState.selectedElements)
        };
        break;
      case 'library':
        result = {
          elements: Array.from(elements.values())
        };
        break;
      case 'theme':
        result = {
          theme: sceneState.theme
        };
        break;
      case 'elements':
        result = {
          elements: Array.from(elements.values())
        };
        break;
      default:
        throw new Error(`Unknown resource: ${resource}`);
    }
    
    return {
      content: [{ type: 'text', text: JSON.stringify(result, null, 2) }]
    };
  }

• src/index.js:75-77 (schema)

  Zod schema used for input validation in the get_resource handler.

  const ResourceSchema = z.object({
    resource: z.enum(['scene', 'library', 'theme', 'elements'])
  });

• src/index.js:171-183 (registration)

  Tool registration in server capabilities, including description and input schema definition.

  get_resource: {
    description: 'Get an Excalidraw resource',
    inputSchema: {
      type: 'object',
      properties: {
        resource: { 
          type: 'string', 
          enum: ['scene', 'library', 'theme', 'elements'] 
        }
      },
      required: ['resource']
    }
  },