app-screen-mcp

Instructions

Implementation Reference

• src/index.ts:627-666 (handler)

  The `takeScreenshot` private method in `src/index.ts` is the handler that performs the screenshot operation and returns the MCP tool response.

  private async takeScreenshot(
    udid?: string,
    maxDimInput?: number,
    qualityInput?: number,
    onlyIfChanged?: boolean,
    previousImageHash?: string
  ) {
    const target = await resolveUdid(udid);
    const options = normalizeScreenshotOptions(maxDimInput, qualityInput);
  
    try {
      const shot = await this.captureScreenshot(target, options);
  
      const compareHash = previousImageHash ?? (
        onlyIfChanged ? this.lastScreenshotHashByUdid.get(target) : undefined
      );
      const changed = compareHash ? compareHash !== shot.hash : true;
  
      this.lastScreenshotHashByUdid.set(target, shot.hash);
  
      const meta = {
        udid: target,
        hash: shot.hash,
        previous_hash: compareHash ?? null,
        changed,
        included: changed,
        source_width: shot.sourceWidth,
        source_height: shot.sourceHeight,
        sent_width: shot.sentWidth,
        sent_height: shot.sentHeight,
        max_dim: shot.maxDim,
        quality: shot.quality,
      };
  
      const content: any[] = [{ type: 'text', text: JSON.stringify(meta, null, 2) }];
      if (changed) {
        content.push({ type: 'image', data: shot.base64, mimeType: 'image/jpeg' });
      }
  
      return { content };

• src/index.ts:336-336 (registration)

  The `take_screenshot` tool is registered in the list of available MCP tools within the initialization of the server in `src/index.ts`.

  name: 'take_screenshot',