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 agentmods add skills/kastheco/claude-plugins/browsernpx skills add kastheco/claude-plugins --skill browsergit clone --depth 1 https://github.com/kastheco/claude-pluginsWhat 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 | $0.00000 | $0.00938 |
| Opus 5 | $0.00000 | $0.00469 |
| Sonnet 5 | $0.00000 | $0.00188 |
| Haiku 4.5 | $0.00000 | $0.00094 |
Grade A, and why
browser scanned grade A with 0 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 2d 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.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 160 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Browser Automation Skill
This skill handles browser automation tasks using subagent architecture to keep the main context window clean.
Core Principle
NEVER call Claude-in-Chrome MCP tools directly in main context.
All browser automation is delegated to the browser-automation Task subagent which returns concise summaries.
Detection Triggers
Activate this skill when detecting:
Web Testing
- "test the website", "check the page", "verify the UI"
- "screenshot", "capture the screen", "take a picture"
- "does the site work", "is the page loading"
Form Automation
- "fill out the form", "submit this form", "enter data"
- "sign up", "register", "create account" (with explicit user permission)
- "login", "authenticate" (without entering passwords directly)
Data Extraction
- "scrape this page", "extract data from", "get the text"
- "what's on the page", "read the content", "parse the data"
- "find the price", "get the title", "extract the links"
Workflow Automation
- "automate this workflow", "record these steps", "create a GIF"
- "click through", "navigate to", "go to page"
- "test the flow", "verify the process"
Debugging & Monitoring
- "check console logs", "monitor network requests", "debug the page"
- "why is this failing", "what's the error", "inspect the page"
Subagent Delegation Pattern
When a browser automation task is detected:
Task("Browser: {brief_description}
**Task:** {user_request}
**URL:** {target_url if provided}
**Actions:** {list of expected actions}
Using Claude-in-Chrome MCP tools:
1. Start with tabs_context_mcp to get current tab state
2. Create new tab or use existing based on context
3. Navigate, interact, extract data as needed
4. Capture screenshots/GIFs for multi-step workflows
5. Monitor console/network if debugging
Return ONLY a concise summary:
- Actions taken (e.g., "Navigated to X, filled form, clicked submit")
- Key findings (e.g., "Form submitted successfully", "Error: XYZ")
- Screenshots/visual evidence if captured
- Any errors or unexpected behavior
Do NOT include:
- Raw HTML or page source
- Verbose console logs (use pattern filtering)
- Detailed network request payloads
- Implementation details
subagent_type: browser-automation
")
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.
- 2d ago First seen · 160 lines · 0 tokens per session scan A c72143146298
browser is a skill published in the GitHub repository kastheco/claude-plugins (2 stars, last pushed 4mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 938 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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