mcp-painter

Instructions

Implementation Reference

• index.ts:87-105 (handler)

  MCP tool handler case that processes the drawing_generateCanvas tool call, invokes the generateCanvas helper, and returns success/error response.

  case "drawing_generateCanvas":
    try {
      currentCanvas = drawingTool.generateCanvas(args.width, args.height);
      return {
        content: [{
          type: "text",
          text: `Canvas generated with width: ${args.width}, height: ${args.height}`,
        }],
        isError: false,
      };
    } catch (error) {
      return {
        content: [{
          type: "text",
          text: `Failed to generate canvas: ${(error as Error).message}`,
        }],
        isError: true,
      };
    }

• drawingTool.ts:105-107 (helper)

  Core helper function that creates and returns a new Canvas instance with the specified dimensions.

  function generateCanvas(width: number, height: number): Canvas {
      return new Canvas(width, height);
  }

• index.ts:22-33 (registration)

  Tool registration object in the TOOLS array used for ListToolsRequest, includes name, description, and input schema.

  {
    name: "drawing_generateCanvas",
    description: "Generate a new drawing canvas with specified width and height.",
    inputSchema: {
      type: "object",
      properties: {
        width: { type: "number", description: "Width of the canvas in pixels" },
        height: { type: "number", description: "Height of the canvas in pixels" },
      },
      required: ["width", "height"],
    },
  },

• drawingTool.ts:12-31 (helper)

  Canvas class definition with constructor that initializes pixel array to white background, used by generateCanvas.

  class Canvas {
      width: number;
      height: number;
      pixels: Pixel[][];
  
      constructor(width: number, height: number) {
          if (typeof width !== 'number' || width <= 0 || typeof height !== 'number' || height <= 0) {
              throw new Error("Canvas dimensions must be positive numbers.");
          }
          this.width = width;
          this.height = height;
          this.pixels = [];
          for (let y = 0; y < height; y++) {
              this.pixels[y] = [];
              for (let x = 0; x < width; x++) {
                  // Default to white background
                  this.pixels[y][x] = { r: 255, g: 255, b: 255, a: 255 };
              }
          }
      }