Chrome DevTools MCP is an MCP server that lets coding agents control and inspect a live Chrome browser for automation, debugging, screenshots, network analysis, console inspection, and performance tracing. It is for developers who want AI coding assistants to test and diagnose web applications, and the catalogue add-ons provide workflows for using those browser tools.
Borrowing it
Nothing to install: this file belongs to ChromeDevTools/chrome-devtools-mcp. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/ChromeDevTools/chrome-devtools-mcp/main/AGENTS.mdgit clone --depth 1 https://github.com/ChromeDevTools/chrome-devtools-mcpWrote 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/instructions/chromedevtools/chrome-devtools-mcp/agents-md)<a href="https://agentmods.dev/instructions/chromedevtools/chrome-devtools-mcp/agents-md"><img src="https://agentmods.dev/badge/instructions/chromedevtools/chrome-devtools-mcp/agents-md/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/instructions/chromedevtools/chrome-devtools-mcp/agents-md"><img src="https://agentmods.dev/badge/instructions/chromedevtools/chrome-devtools-mcp/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00971 | $0.00971 |
| Opus 5.5 | $0.00388 | $0.00388 |
| Sonnet 5.5 | $0.00194 | $0.00194 |
| Haiku 4.5 | $0.00097 | $0.00097 |
Grade A, and why
chrome-devtools-mcp AGENTS.md 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 1mo 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.
Copies of this mod
8 near-identical copies found in the catalogue:
- chrome-devtools-mcp AGENTS.md — 100% identical, 37 lines differ
- brave-devtools-mcp AGENTS.md — 100% identical, 0 lines differ
- arc-devtools-mcp AGENTS.md — 92% identical, 38 lines differ
- chrome-devtools-mcp AGENTS.md — 92% identical, 38 lines differ
- Chrome_Auto_Mcp AGENTS.md — 92% identical, 38 lines differ
- chrome-devtools-mcp AGENTS.md — 92% identical, 38 lines differ
- chrpme_MCP AGENTS.md — 92% identical, 38 lines differ
- chrome-devtools-mcp AGENTS.md — 92% identical, 38 lines differ
How it starts
The opening of the file, as written. The whole thing — 58 lines — stays where its author put it; the contents beside it link to each section on GitHub.
This repository contains an MCP server and CLI for Chrome DevTools.
Instructions
- Use only scripts from
package.jsonto run commands. - Use
npm run buildto run tsc and test build. - Use
npm run testto build and run tests, run all tests to verify correctness. - Use
npm run test path-to-test.tsto build and run a single test file, for example,npm run test tests/McpContext.test.ts. - Use
npm run formatto fix formatting and get linting errors. - Never modify
third_party/devtools-frontendexcept for experimentation: it is a git submodule, a mirror of the actual codebase.
Rules for TypeScript
- Do not use
anytype. - Do not use
askeyword for type casting. - Do not use
!operator for type assertion. - Do not use
// @ts-ignorecomments. - Do not use
// @ts-nocheckcomments. - Do not use
// @ts-expect-errorcomments. - Prefer
for..ofinstead offorEach. - Never type-check types that are already type safe (e.g. redundant
typeofchecks on statically typed variables).
Rules for Testing
Structure and Separation of Concerns
- Prefer mock-based unit tests over real-browser tests: Do not use
withMcpContextor launch a real browser unless the test genuinely requires real browser or DevTools protocol integration (e.g., live CDP events, browser lifecycle, secondary sessions). Puppeteer already tests browser behavior upstream; unit tests run faster and avoid browser overhead. - Tool handler tests (
tests/tools/*.test.ts):- Test that the tool handler parses/validates parameters and invokes the corresponding methods on
page,context, orresponsewith the exact expected arguments. - Do not reimplement business logic or state tracking inside mocks (e.g., do not simulate state changes in mock methods).
- Test that the tool handler parses/validates parameters and invokes the corresponding methods on
- Core class tests (e.g.,
tests/McpPage.test.ts):- Test business logic by instantiating the real class under test with mocked dependencies (e.g., instantiate
new McpPage(...)with a mocked Puppeteer page fromcreateMockPuppeteerPage()). - Assert that the class calls the underlying Puppeteer methods with the expected parameters.
- Test business logic by instantiating the real class under test with mocked dependencies (e.g., instantiate
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.
- 1mo ago Changed · +37 lines · +735 tokens per session 1b804c2b806a
- 1mo ago First seen · 21 lines · 236 tokens per session scan A 9087ba513381
chrome-devtools-mcp AGENTS.md is an instructions file published in the GitHub repository ChromeDevTools/chrome-devtools-mcp (53,735 stars, last pushed today), licensed Apache-2.0. It adds 971 tokens to every session, about $0.0039 per session on Opus 5.5. 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 2026-08-30.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
deepseek-harness AGENTS.md
AGENTS.md instructions for deepseek-ai/deepseek-harness, covering agents.md, pre-stable apis and released session data, repository layout, commands and host sandbox failures.
vscode copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).