nakkas

Instructions

Implementation Reference

• src/index.ts:189-207 (handler)

  The handler logic for the 'preview' tool which calls `renderPreview` and returns the base64 encoded PNG image.

  async ({ content, format, width }) => {
    const start = Date.now();
    try {
      const pngBuffer = renderPreview(content, format, width);
      const base64 = pngBuffer.toString("base64");
      const elapsed = Date.now() - start;
      console.error(`[nakkas] preview OK — ${pngBuffer.length} bytes, ${elapsed}ms`);
      return {
        content: [{ type: "image", data: base64, mimeType: "image/png" }],
      };
    } catch (err) {
      const message = err instanceof Error ? err.message : String(err);
      console.error(`[nakkas] preview ERROR — ${message}`);
      return {
        content: [{ type: "text", text: `Error rendering preview: ${message}` }],
        isError: true,
      };
    }
  }

• src/index.ts:154-188 (registration)

  The registration of the 'preview' MCP tool including its description and input schema.

  server.registerTool(
    "preview",
    {
      title: "Preview SVG",
      description: `
  Render SVG content to a PNG image so the AI can visually inspect the output.
  
  **When to use:**
  - After render_svg, call preview to see what was generated
  - Use in a revision loop: render → preview → critique → revise → preview again
  - Stop when the visual result matches the intent
  
  **Behavior:**
  - Returns a PNG image (base64) rendered from the SVG string
  - Background is transparent by default
  - CSS animations and SMIL are rendered as a static snapshot (t=0) — motion is not captured
  - Format is auto-detected from content; pass format: "svg" explicitly if needed
  
  **Width:**
  - Omit width to use the SVG's own declared width/viewBox
  - Pass width to scale the output (useful for small SVGs that need a larger preview)
      `.trim(),
      inputSchema: z.object({
        content: z.string().describe("SVG string to render as PNG"),
        format: z
          .enum(["svg", "html"])
          .optional()
          .describe("Content format; auto-detected from content if omitted"),
        width: z
          .number()
          .positive()
          .optional()
          .describe("Render width in pixels; defaults to SVG's own declared width"),
      }),
    },