vnc - SKILL.md Agent Skill

name: vnc description: Control a remote desktop via VNC. Use when user asks to interact with a remote computer screen — click, type, screenshot, scroll, or connect/disconnect VNC sessions. allowed-tools: Bash Read

VNC Computer-Use Tool

You have access to a VNC computer-use CLI tool (vnc) that lets you control a remote desktop. Use it to interact with GUIs — click buttons, type text, take screenshots, scroll, and more.

Installation

If the vnc command is not available, install it first:

pip install vnc-computer-use

Quick Reference

Connect / Disconnect

# Connect to a VNC server
vnc connect <host>::<port>
vnc connect <host>::<port> --password <pw>
vnc connect <host>::<port> --username <user> --password <pw>  # macOS Screen Sharing
vnc connect <host>::<port> --password <pw> --legacy-auth       # macOS legacy VNC password

# Disconnect
vnc disconnect

Screenshots

# Save screenshot to file (preferred — you can then read the image)
vnc get_screenshot -o /tmp/screen.png

# Get screenshot as base64 JSON
vnc get_screenshot

Screenshot response includes image_width and image_height:

{"ok": true, "path": "/tmp/screen.png", "image_width": 1568, "image_height": 882}

Mouse Actions

vnc left_click <x> <y>
vnc right_click <x> <y>
vnc double_click <x> <y>
vnc middle_click <x> <y>
vnc mouse_move <x> <y>
vnc left_click_drag <x> <y>     # drag from current position to (x, y)
vnc scroll <direction> <x> <y>  # direction: up, down, left, right, or down:500

Keyboard Actions

vnc key <key>          # e.g. enter, tab, ctrl-c, alt-f4, shift-a
vnc type "<text>"      # type a string character-by-character

Info

vnc get_screen_size
vnc get_cursor_position
vnc status

Multi-Session

vnc connect host1::5900 --session work
vnc connect host2::5900 --session home
vnc -s work get_screenshot -o /tmp/work.png
vnc -s home left_click 100 200
vnc disconnect --session work

Coordinate System

IMPORTANT: All coordinates are in image space, not raw screen space.

Screenshots are automatically downscaled to fit Claude's vision limits (max 1568px long edge).
The image_width and image_height in the screenshot response tell you the coordinate space.
When you click/move using coordinates, the tool automatically maps them back to the real screen.
get_cursor_position and get_screen_size also return values in image space.

This means: use the coordinates as you see them in the screenshot image directly. No manual scaling needed.

Cursor Crosshair

Screenshots include a red crosshair marking the current cursor position. Use it to:

Verify your last click landed where you intended.
If the crosshair is far from your target, adjust coordinates proportionally to the distance — use large adjustments first, then refine.
Consider the display dimensions when estimating positions (e.g. if something is 90% to the bottom, the y-coordinate should be ~90% of image_height).

Usage Guidelines

For macOS mini-machine legacy VNC passwords, use --legacy-auth when connecting; otherwise vncdotool may choose Apple/DH auth and hang or fail.
Always take a screenshot first before clicking — you need to see where elements are on screen.
Prefer keyboard shortcuts over clicking when possible (faster and more reliable).
Click center of elements — don't click edges of buttons or icons.
Wait and re-screenshot if an action doesn't seem to take effect. GUI apps may need time to respond (a 1-second delay is built into screenshots).
All output is JSON — parse it to check for "ok": true or "error" fields.
Check the crosshair after clicking to verify accuracy. If it missed, adjust.
Coordinates outside screen bounds will return an error.

Workflow Example

A typical interaction looks like:

vnc connect <host>::<port> — establish connection
vnc get_screenshot -o /tmp/screen.png — see what's on screen (also gives you image dimensions)
Read the screenshot to identify UI elements and their coordinates
vnc left_click <x> <y> — click on the target element
vnc get_screenshot -o /tmp/screen.png — verify the result, check crosshair position
If crosshair missed the target, adjust coordinates and retry
Repeat steps 3-6 as needed
vnc disconnect — when done