Screenshot Skill

Take screenshots using macOS screencapture command via Bash.

Important: Always Resize for Context

Full-resolution screenshots (especially on Retina/5K displays) produce huge base64 that will exceed the model's context length. Always resize before reading.

Take and View a Screenshot

# 1. Capture full screen
/usr/sbin/screencapture -x -t jpg /tmp/alma-screenshot.jpg

# 2. Resize to 1024px wide (critical for context size!)
/usr/bin/sips --resampleWidth 1024 --setProperty formatOptions 60 /tmp/alma-screenshot.jpg --out /tmp/alma-screenshot-thumb.jpg 2>/dev/null

# 3. Get dimensions
/usr/bin/sips -g pixelWidth -g pixelHeight /tmp/alma-screenshot.jpg 2>/dev/null

Then use the Read tool to read /tmp/alma-screenshot-thumb.jpg (the resized version, NOT the full-size one).

Capture Options

# Full screen (default)
/usr/sbin/screencapture -x -t jpg /tmp/alma-screenshot.jpg

# Interactive window selection
/usr/sbin/screencapture -x -w -t jpg /tmp/alma-screenshot.jpg

# Specific region (x,y,w,h)
/usr/sbin/screencapture -x -R 0,0,800,600 -t jpg /tmp/alma-screenshot.jpg

# With 3-second delay
/usr/sbin/screencapture -x -T 3 -t jpg /tmp/alma-screenshot.jpg

Send Screenshot to User (Telegram)

If the user wants to see the screenshot directly, use the alma CLI or just describe what you see. The full-resolution file is at /tmp/alma-screenshot.jpg.

Tips

• Always resize before reading into context — use the thumb version
• -x flag suppresses the capture sound
• -t jpg outputs JPEG (smaller than PNG)
• Use sips --setProperty formatOptions 60 for higher compression if needed