Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add markus-global/markus --skill chrome-devtoolsgit clone --depth 1 https://github.com/markus-global/markusWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/markus-global/markus/chrome-devtools)<a href="https://agentmods.dev/skills/markus-global/markus/chrome-devtools"><img src="https://agentmods.dev/badge/skills/markus-global/markus/chrome-devtools/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/markus-global/markus/chrome-devtools"><img src="https://agentmods.dev/badge/skills/markus-global/markus/chrome-devtools.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 5 findings, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Tool Misuse · line 109 Tool calls are chained to bypass individual safety checks or escalate capabilities beyond what any single tool call would allow.Fix: Limit tool chaining depth and validate the output of each tool before passing it to the next. Require explicit user approval for multi-step chains.
- high Tool Misuse · line 109 Tool calls are chained to bypass individual safety checks or escalate capabilities beyond what any single tool call would allow.Fix: Limit tool chaining depth and validate the output of each tool before passing it to the next. Require explicit user approval for multi-step chains.
- high YARA Match · line 315 YARA rule matched a known malware signature (reverse shell, backdoor, ransomware, C2 framework, or info stealer).Fix: Remove the malware payload or compromised file entirely. Investigate how it entered the skill and audit all other artifacts for additional indicators of compromise.
- medium MCP Rug Pull · line 83 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium Privilege Escalation · line 109 Commands invoke sudo or root privileges. Verify this elevated access is necessary and justified.Fix: Avoid sudo/root unless strictly required. Prefer least-privilege patterns. If elevation is needed, document the justification and scope.
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00017 | $0.04850 |
| Opus 5.5 | $0.00007 | $0.01940 |
| Sonnet 5.5 | $0.00003 | $0.00970 |
| Haiku 4.5 | $0.00002 | $0.00485 |
Grade B, and why
chrome-devtools scanned grade B with 2 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 27d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Asks for rootmediumPrivilege escalation
A mod that escalates privileges can change anything on the machine, not only the project.
- **Linux (Debian/Ubuntu)**: `wget -q -O - https://dl.google.com/linux/linux_signing_key.pub | sudo apt-key add - && sudo apt update && sudo apt install google-chrome-stable` Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
- **Linux (Debian/Ubuntu)**: `wget -q -O - https://dl.google.com/linux/linux_signing_key.pub | sudo apt-key add - && sudo apt update && sudo apt install google-chrome-stable` How it starts
The opening of the file, as written. The whole thing — 428 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Chrome DevTools Browser Automation
You have access to a live Chrome browser via Chrome DevTools MCP tools (prefixed chrome-devtools__).
This gives you full browser automation: navigation, clicking, typing, screenshots, JS evaluation,
network inspection, and performance profiling.
When to use these tools
Use Chrome DevTools tools when you need to:
- Interact with web pages (click buttons, fill forms, navigate)
- Test web applications in a real browser
- Take screenshots of pages or elements
- Inspect console logs, network requests, or page structure
- Run Lighthouse audits or performance traces
- Debug frontend issues with live DOM inspection
Do NOT use these tools when web_fetch or web_search suffice (simple content retrieval or search).
Chrome DevTools is for interactive browser sessions that require a real rendering engine.
Connection Modes
Markus supports three ways to connect to Chrome, listed from best to fallback:
Mode 1: Markus Chrome Extension (recommended)
The Markus Browser Automation Chrome extension provides the smoothest experience:
- No debugging dialog — the extension uses
chrome.debuggerAPI internally - Works when screen is locked or sleeping — no OS-level interaction needed
- Cross-platform — works on macOS, Windows, and Linux identically
- Instant startup — no
npxdownload, no child process spawn - No extra permissions — no macOS Accessibility or Windows UI Automation needed
How to install:
- Build the extension (one-time):
cd packages/chrome-extension && pnpm install && pnpm run build - Open Chrome →
chrome://extensions/ - Enable Developer mode (toggle in top-right)
- Click Load unpacked → select
packages/chrome-extension/dist - The Markus icon appears in the toolbar
How it works:
When Markus starts, it launches a WebSocket bridge on ws://127.0.0.1:9333. The extension
auto-connects to this bridge. All browser tool calls are routed through the extension instead
of spawning an external MCP process.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 27d ago Changed · +55 lines 49b55f734e27
- 1mo ago First seen · 373 lines · 17 tokens per session scan B c77906ee46b8
chrome-devtools is a skill published in the GitHub repository markus-global/markus (205 stars, last pushed today), licensed Apache-2.0. It adds 17 tokens to every session and 4,850 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it B with 2 findings (asks for root, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
peekaboo
Capture and automate macOS UI with the Peekaboo CLI.
agent-browser
Automates browser interactions for web testing, form filling, screenshots, and data extraction. Use when the user needs to navigate websites, interact with web pages, fill forms, take screenshots, test web applications, or extract information from web pages.
x-scraper
A scraper for X, formerly called Twitter, that collects posts from a chosen user's timeline or the signed-in home feed. It can filter by keyword and export Markdown, RSS, or JSON.
html-to-image
A tool that renders an HTML file or HTML text in a browser and saves the result as a PNG image. HTML is the markup used to structure web pages and visual layouts.
xhs-publisher
A browser-automation workflow for publishing image posts to Xiaohongshu, a Chinese social-media platform often used for lifestyle and product content. It fills in the title and text, uploads one or more images, and publishes through the creator centre.
xhs-scraper
A scraper for Xiaohongshu, a Chinese social-media platform, that uses a connected browser to collect search results and, optionally, post details. It can save the results as Markdown, RSS, or JSON.