Built an open source WebMCP Inspector (a web-app, not an extension)

[Sasha Ogurtov]

Hey everyone!

I built WebMCP Inspector — a web app (not a browser extension) for inspecting, debugging, and augmenting WebMCP tools on any webpage in real time. It runs entirely in the browser using sandboxed Webfuse sessions — just paste a  URL and start inspecting, no install required.

It discovers both declarative (HTML form-based) and imperative (JS API via navigator.modelContext/navigator.modelContextTesting) tools, and lets you:

- View generated JSON schemas for discovered tools
- Edit WebMCP attributes on any form (or add them to plain forms)
- Execute tools directly from the sidebar with typed parameter inputs
- Test with Chrome's on-device Gemini Nano model through a built-in Prompt Debugger — the on-device agent discovers and calls tools based on natural language prompts
- Track everything in a real-time activity log

Target pages render in a sandboxed browser session powered by Webfuse, so there's no browser extension to install — just paste a URL and start inspecting.

Live demo: https://webmcpinspector.com/
Source: https://github.com/aogz/webmcpinspector (MIT)

Would love to hear any feedback or ideas. Happy to answer questions!