nib

Original：🇺🇸 English
Translated

Visual feedback from humans via screenshot annotations. Use this skill CONSTANTLY — any time you need visual context, want to verify UI changes, need to confirm layout, debug a visual issue, check styling, validate a design, or show your work. Capture the screen, look at it, figure out what you need feedback on, annotate it, and ask. Do not ask the user what to capture — just capture and look.

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Sourcedouglance/nib
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NPX Install

npx skill4agent add douglance/nib nib

Tags

Translated version includes tags in frontmatter
screenshot-annotationvisual-feedbacknib-toolui-validationcommand-line-utility

SKILL.md Content

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Nib — Visual Feedback

You have eyes. Use them. Any time something visual is relevant, capture the screen and look.

When to Use This

Use nib aggressively. If any of these apply, capture and look:
  • You just made a UI change → capture and verify it looks right
  • You're debugging something visual → capture and inspect
  • You need to know where something is on screen → capture and find it
  • You're unsure about layout, spacing, colors, alignment → capture and check
  • The user mentions anything visual → capture immediately
  • You want to show the user what you did → capture and annotate
  • You're about to ask "does this look right?" → capture instead of asking
  • You need coordinates for clicking or positioning → capture and use grid
Don't ask what to capture. Don't ask permission. Just capture and look.

The Loop

1. Find the right window → nib windows --json
2. Capture it → nib capture --app "AppName" -o /tmp/nib_shot.png
3. Look at the screenshot (read the file)
4. Decide what you need feedback on
5. nib feedback /tmp/nib_shot.png -a '[annotations]' -m "question"
6. Parse the human's response
7. Act on it

Step 1: Find the Right Window

Don't just screenshot everything. Find the window you actually care about:
bash
# List all windows with metadata
nib windows --json

# Filter by app name
nib windows --app "Safari" --json
Output gives you app name, title, size, position, and focus state for every window.

Step 2: Capture the Right Thing

bash
# Capture a specific app's window
nib capture --app "Safari" -o /tmp/nib_shot.png

# Capture by window title
nib capture --title "index.html" -o /tmp/nib_shot.png

# Capture the focused window
nib capture --mode window -o /tmp/nib_shot.png

# Capture full screen (fallback)
nib capture -o /tmp/nib_shot.png
Always prefer 
--app
or 
--title
over full screen. You get just the window you need, no distractions.

Step 3: Look

Read the screenshot file to see what's on screen. Use grid or OCR if you need precision:
bash
# Coordinate grid for positioning
nib grid /tmp/nib_shot.png --spacing 100 -o /tmp/nib_grid.png

# Find text via OCR
nib find-text /tmp/nib_shot.png -s "Submit"

Step 3: Annotate and Ask

Point at the things you want feedback on. Be specific.
bash
nib feedback /tmp/nib_shot.png \
  -a '[{"type":"arrow","from":[300,200],"to":[450,350]},{"type":"text","at":[300,180],"content":"This spacing looks off?"}]' \
  -m "Does the spacing between these elements look right?"

Step 4: Parse Response

Human draws annotations and hits Cmd+Enter. You get back only their annotations:
json
{"annotations": [{"id": "a1", "type": "arrow", "at": [150, 200, 300, 100], "owner": "human"}]}
Timeout returns 
{"event": "timeout"}
(exit code 0, not an error).

Step 5: Act

Use the human's visual feedback to take action. Then capture again to verify.

Annotation Format

json
[
  {"type": "arrow", "from": [x, y], "to": [x, y]},
  {"type": "rectangle", "at": [x, y], "size": [w, h]},
  {"type": "text", "at": [x, y], "content": "Label"},
  {"type": "highlight", "at": [x, y], "size": [w, h], "color": "#ffff0080"},
  {"type": "number", "at": [x, y], "value": 1},
  {"type": "ellipse", "center": [x, y], "radius": [rx, ry]},
  {"type": "line", "from": [x, y], "to": [x, y]},
  {"type": "blur", "at": [x, y], "size": [w, h]}
]
All types accept optional 
"color"
(hex). Use blue 
#3b82f6
for your annotations.

Headless Mode

When you don't need human feedback, just annotate and render:
bash
nib annotation add image.png -t rectangle -x 100 -y 100 -w 200 -H 50 -c "#ff0000"
nib render image.png  # → image.rendered.png

Key Flags

CommandFlagPurpose
capture
--app
Capture specific app's window
capture
--title
Capture window by title substring
capture
--mode window
Capture focused window
windows
--app
Filter window list by app name
windows
--json
Machine-readable window list
feedback
-a
JSON annotations array
feedback
-m
Message/question as toast
feedback
-t
Timeout in seconds (default 60)
find-text
-s
Search string
find-text
--highlight --color
Auto-highlight matches (NOT 
-c
)
grid
--spacing
Grid cell size in pixels
grid
--region
Zoom to region (x1,y1,x2,y2)
See full command reference for all commands and options.