spm1001/screenshot

Screenshotting

Take screenshots to see what's on screen. Captures persist as files (unlike browsermcp snapshots which only exist in context).

Quick Reference

# Capture specific app window
${CLAUDE_SKILL_DIR}/scripts/look.py --app Ghostty

# Capture window by title match
${CLAUDE_SKILL_DIR}/scripts/look.py --app Chrome --title "LinkedIn"

# Capture full screen
${CLAUDE_SKILL_DIR}/scripts/look.py --screen

# List available windows
${CLAUDE_SKILL_DIR}/scripts/look.py --list

# List windows grouped by category
${CLAUDE_SKILL_DIR}/scripts/look.py --categories

# List only browser windows
${CLAUDE_SKILL_DIR}/scripts/look.py --category browsers

# Native resolution (skip resize)
${CLAUDE_SKILL_DIR}/scripts/look.py --app Safari --native

Categories: browsers, terminals, editors, communication, documents, media, other

When to Use

Reactive (user asks):

• "Have a look at this"
• "Can you see what's on screen?"
• "What does it look like?"
• "Check the browser"

Proactive (verify state):

• After uncertain CLI operations (did it background?)
• When tool prompt state is unclear
• After browsermcp actions when snapshot isn't enough
• To verify visual changes actually happened

Documentation:

• Capture steps in a workflow
• Before/after comparisons
• Bug evidence with screenshots

When NOT to Use

• Browser-only tasks where browsermcp snapshot suffices
• When you just need to describe what's visible
• High-frequency captures that would clutter the directory

Anti-Patterns

| Pattern | Problem | Fix | |---------|---------|-----| | Capture without purpose | Clutters context | Only screenshot when you need the visual | | Skip --list first | Wrong window captured | List windows to find exact app/title | | Native on large screens | Huge files, slow upload | Use default 1568px resize |

Resolution Strategy

Default: 1568px max dimension (~1,600 tokens, optimal for API)

| Option | Tokens | Use case | |--------|--------|----------| | Default (1568px) | ~1,600 | Full detail, no resize penalty | | --max-size 735 | ~500 | Quick look, text readable | | --native | varies | When original resolution needed |

Why 1568px: Images larger than this get resized server-side anyway. Pre-resizing avoids upload latency while getting the same visual fidelity.

Output

Ephemeral (no path): Screenshots go to /tmp/claude-screenshots/ — auto-cleaned by OS, won't clutter project directories:

/tmp/claude-screenshots/2025-12-15-143022-chrome.png

Persistent (explicit path): For documentation workflows, specify where screenshots should live:

look.py --app Chrome ./docs/step3.png

Design rationale: Quick looks are ephemeral by default. Documentation requires intentional placement. If a subagent is documenting, it should think about where artifacts belong.

How It Works

1. Window enumeration: Uses macOS CGWindowList API (pure Quartz, no AppleScript)
2. Capture: Uses screencapture -l<windowid> for windows, screencapture -x for screen
3. Resize: Uses sips --resampleHeightWidthMax for efficient scaling

Key capability: Can capture windows even when covered or minimized.

Limitations

Scrollback: Only captures visible viewport. If content scrolled off screen, it won't be in the screenshot. Workaround: increase window size or pipe output to file.

Multiple monitors: Untested. --screen with -m flag captures main monitor only.

Window selection: Takes first match when multiple windows match filters. No "frontmost" heuristic yet.

Integration with browsermcp

browsermcp's browser_screenshot injects images directly into context but doesn't persist them as files. Use this skill when you need:

• Screenshots that persist beyond the conversation
• Captures of non-browser apps
• Captures of windows behind the browser
• Files to upload to Drive or include in docs

Permissions

Requires Screen Recording permission in System Preferences > Privacy & Security.

If capture fails with "check Screen Recording permissions", the user needs to grant permission to the terminal app (Ghostty, Terminal, iTerm, etc.).