h5-devtools-mcp

h5-devtools-mcp

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An MCP server that lets coding agents (Claude Code, Codex, Cursor…) debug H5 pages running inside Android WebViews on real devices — read console output and uncaught exceptions, and run JavaScript in the page, without opening chrome://inspect.

Status: v0.1, early. Android only.

How it works

Coding agent ──MCP (stdio)──▶ h5-devtools-mcp ──adb forward──▶ webview_devtools_remote_<pid> ──CDP──▶ WebView page

Every debuggable WebView exposes a Chrome DevTools Protocol endpoint on an abstract unix socket. The server discovers those sockets over adb (the same way chrome://inspect does), forwards them to local ports, and connects with CDP.

Requirements

• Node.js 18+
• adb on your PATH (or set ADB_PATH)
• An Android device with USB debugging enabled
• The app must enable WebView debugging (debug builds usually do):

WebView.setWebContentsDebuggingEnabled(true);

Setup

# Claude Code
claude mcp add h5-devtools -- npx -y h5-devtools-mcp

Other MCP clients (Cursor, Codex…) take the same command: npx -y h5-devtools-mcp.

From source

git clone https://github.com/xianguoGou/h5-devtools-mcp.git
cd h5-devtools-mcp
npm install && npm run build
claude mcp add h5-devtools -- node /absolute/path/to/h5-devtools-mcp/dist/index.js

Tools

Tool	What it does
list_targets	List debuggable pages: app package, title, URL, visibility
attach	Connect to a page and start buffering console output
get_console	Read buffered entries, filtered by level / keyword / exclude_keywords, incrementally via since_seq
evaluate_js	Run a JavaScript expression in the page and return the result (promises are awaited)
detach	Disconnect from a page

Output is designed to be token-cheap: compact one-line entries, long messages truncated, and since_seq so an agent only reads what's new instead of re-reading the whole buffer on every turn.

Example

> list_targets
- id: R5CT1234/webview_devtools_remote_8812/3A1F…
  app: com.example.app (pid 8812) on SM-S9180
  title: "Order"
  url: https://m.example.com/order

> get_console { "levels": ["error"] }
#41 10:32:01.123 [error exception] TypeError: Cannot read properties of undefined (reading 'price')
    at https://m.example.com/assets/index-8f2a.js:1:48213
next since_seq: 57

Troubleshooting

• "no debuggable WebView found" — the app hasn't enabled WebView debugging, or no WebView is alive yet. Open the H5 page first.
• "debugger in use" — only one debugger can attach to a page. Close the chrome://inspect DevTools window.
• "unauthorized" — accept the USB debugging prompt on the device.

Known limitations

• Debugger-in-use detection is best-effort. It relies on /json/list omitting webSocketDebuggerUrl. Recent Chromium accepts several CDP clients per page, so attach may succeed alongside an open DevTools window; older WebViews may still refuse.
• list_targets can take ~3s per unresponsive app. Sockets are queried one by one with a 3s timeout, and Android freezes background apps, so their WebView sockets stop answering. attach only re-checks the target's own socket and stays fast.
• evaluate_js runs with the page's full privileges — it can read cookies, storage and tokens, and change page state. Keep it behind your agent's tool-permission prompt.
• The e2e script expects port 9333 to be free. If a previous run left a headless Chromium behind, it attaches to that one; kill it first.

Development

The e2e test uses a fake adb and headless Chromium in place of a phone:

npm run build
CHROME=/path/to/chrome npm run test:e2e

Roadmap

• Discover devices and WebView pages
• Console messages, uncaught exceptions, browser log entries
• Network requests and responses
• JSBridge call logging (configurable bridge shapes)
• evaluate_js
• screenshot
• JSBridge mocking
• iOS (WKWebView via WebKit Inspector Protocol)

License

MIT