Web Browser Agent Skill

Automate web pages through Chrome via the Chrome DevTools Protocol: navigate, click, fill forms, inspect content, take screenshots, and…

Context cost
1.7k tokensestimated from the bundle, loaded when it triggers
Bundle
16 files · 72.1 kB13 scripts among them — read before you run
Licence
Stolen from Mariothe author’s own terms
Last change
—no release on file
Servers it uses
Noneruns standalone

What it does

Automate and interact with web pages through Chrome or Chromium using the Chrome DevTools Protocol (CDP): navigate, click, fill forms, inspect content, take screenshots, and debug console or network activity. Use when an agent needs a real browser. Prefer headless Chrome unless visible browser interaction is required.

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

browsercdpchromescreenshots

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md5.8 kB · preview
--- name: web-browser license: Stolen from Mario ---
7# Web Browser Skill
8
9Minimal CDP tools for collaborative site exploration.
10
11## Start Chrome (Prefer Headless)
12
13```bash
14./scripts/start.js --headless # Recommended: isolated reusable profile
15./scripts/start.js --headless --profile # Headless with a copy of your profile
16./scripts/start.js # Visible browser window when needed
17./scripts/start.js --headless --reset-profile # Clear cached profile before launch
18```
19
20Starts Chrome with remote debugging (default port :9222). **Agents should use --headless by default** because it is less disruptive and supports navigation, evaluation, screenshots, emulation, and logging. User extensions are disabled for headless launches; a copied profile still provides its cookies and other browser state, but extension-based features are unavailable. Headed launches continue to load extensions normally. Use headed mode only when a person needs to see or interact with the browser, such as for pick.js, manual authentication, or debugging a headless-specific difference.
21
22The start script only reuses a running browser when its profile and launch settings match. Stop the running skill browser before switching between headless and headed mode. Changing the debugging port does **not** isolate the profile: startup refuses to modify a profile already used on another port and preserves Chrome's profile locks.
23
24Profile behavior:
25- Default mode uses: ~/.cache/agent-web/browser/fresh-profile
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md681 words
Files16
LicenceStolen from Mario
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈100
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
1,575
on trigger
The instruction body and 15 supporting files, read only when the skill fires.
0.84%
of a 200k window
Ten skills this size would take about 8% of the window before you open a file.
050k100k150k200k context window

1.7k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Middling. Fine to keep on in a project where you use it weekly, worth unloading in one where you never do.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

Its SKILL.md does not declare which tools it asks the agent for, so what it touches is whatever the instructions themselves ask for — read them before you install it.

What it asks for
Writes filesnot declared
Network accessnot declared

This SKILL.md carries no allowed-tools line, so neither is declared. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

16 files, 72.1 kB on disk. Mostly text — the instructions the model reads — with 13 scripts in it that your client would run only if the instructions tell it to.

  • SKILL.md5.8 kB
  • scripts/cdp.js7.6 kB
  • scripts/devices.js3.5 kB
  • scripts/dismiss-cookies.js14.5 kB
  • scripts/emulate.js3.6 kB
  • scripts/emulation-state.js2.0 kB
  • scripts/eval.js2.3 kB
  • scripts/logs-tail.js1.9 kB
  • scripts/nav.js1.9 kB
  • scripts/net-summary.js2.6 kB
  • scripts/package.json0.1 kB
  • scripts/package-lock.json0.8 kB
  • scripts/pick.js5.7 kB
  • scripts/screenshot.js4.5 kB
  • scripts/start.js7.9 kB
  • scripts/watch.js7.4 kB
What is not in it

A skill installs nothing and depends on nothing: it is a folder your client reads. This one carries 13 scripts beside the text, so the bundle is 16 files you can review in full before installing. The licence the author declares covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# Web Browser · 1.7k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/web-browser/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/web-browser" ] && { [ ! -e .claude/skills/web-browser ] || { mv .claude/skills/web-browser "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/web-browser" .claude/skills/ && echo "Installed .claude/skills/web-browser"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add mitsuhiko/web-browser

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/web-browser/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/web-browser/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/web-browser" ] && { [ ! -e ~/.claude/skills/web-browser ] || { mv ~/.claude/skills/web-browser "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/web-browser" ~/.claude/skills/ && echo "Installed ~/.claude/skills/web-browser" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/web-browser/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Versionnot versioned
Publishedno release date on file
PriceFree
Referencemitsuhiko/web-browser

Versions

Its author publishes no version number, so there is nothing here to pin to: what you install is the folder as it stands today. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

Pinning

Nothing to pin to: this skill carries no version number of its own. What you install is what the folder holds on the day you install it.

Reviews

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