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/googlecloudplatform/scion/chrome-devtoolsnpx skills add GoogleCloudPlatform/scion --skill chrome-devtoolsgit clone --depth 1 https://github.com/GoogleCloudPlatform/scionWhat 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 | $0.00038 | $0.00489 |
| Opus 5 | $0.00019 | $0.00244 |
| Sonnet 5 | $0.00008 | $0.00098 |
| Haiku 4.5 | $0.00004 | $0.00049 |
Grade A, and why
chrome-devtools 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.
This is a copy
83% identical to chrome-devtools — 36 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
What it actually says
Core Concepts
Browser lifecycle: Browser starts automatically on first tool call using a persistent Chrome profile. Configure via CLI args in the MCP server configuration: npx chrome-devtools-mcp@latest --help.
Page selection: Tools operate on the currently selected page. Use list_pages to see available pages, then select_page to switch context.
Element interaction: Use take_snapshot to get page structure with element uids. Each element has a unique uid for interaction. If an element isn't found, take a fresh snapshot - the element may have been removed or the page changed.
Workflow Patterns
Before interacting with a page
- Navigate:
navigate_pageornew_page - Wait:
wait_forto ensure content is loaded if you know what you look for. - Snapshot:
take_snapshotto understand page structure - Interact: Use element
uids from snapshot forclick,fill, etc.
Efficient data retrieval
- Use
filePathparameter for large outputs (screenshots, snapshots, traces) - Use pagination (
pageIdx,pageSize) and filtering (types) to minimize data - Set
includeSnapshot: falseon input actions unless you need updated page state
Tool selection
- Automation/interaction:
take_snapshot(text-based, faster, better for automation) - Visual inspection:
take_screenshot(when user needs to see visual state) - Additional details:
evaluate_scriptfor data not in accessibility tree
Parallel execution
You can send multiple tool calls in parallel, but maintain correct order: navigate → wait → snapshot → interact.
Troubleshooting
If chrome-devtools-mcp is insufficient, guide users to use Chrome DevTools UI:
If there are errors launching chrome-devtools-mcp or Chrome, refer to https://github.com/ChromeDevTools/chrome-devtools-mcp/blob/main/docs/troubleshooting.md.
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 · 46 lines · 38 tokens per session scan A d7e79222debb
chrome-devtools is a skill published in the GitHub repository GoogleCloudPlatform/scion (1,683 stars, last pushed 2d ago), licensed Apache-2.0. It adds 38 tokens to every session and 489 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 83% identical to chrome-devtools, differing in 36 lines, and is treated as a copy.
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