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The WebMCP Inspector is a Chrome extension that inspects the WebMCP server a web page exposes. It opens as a side panel next to the page, lists the tools that page registers, and lets you call them with typed inputs and read the results without leaving the tab. Reach for it when you are building WebMCP into a website and need to answer questions like:
  • Are my tools actually registered, and with the schemas I expect?
  • Does a tool run correctly with a given set of parameters?
  • Do tools appear and disappear as they should when the page state or route changes?
It is built with WXT, React, and TypeScript, and reuses components from the mcp-use Inspector. Unlike the Inspector, it does not connect to remote MCP servers — it only talks to the WebMCP API of the page in the active tab. The source lives at mcp-use/webmcp-inspector.
WebMCP is experimental. If the API is unavailable on a page, enable WebMCP for testing in chrome://flags and relaunch a compatible Chromium build.

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Install the prebuilt build

The extension is not on the Chrome Web Store. Download the prebuilt zip and load it unpacked:
1

Download the build

Grab webmcp-inspector.zip. That link always serves the latest release. Unzip it somewhere you can keep it — Chrome loads the unpacked folder from disk.
2

Enable Developer mode

Open chrome://extensions and turn on Developer mode.
3

Load unpacked

Click Load unpacked and select the unzipped folder.
4

Open the panel

Open a WebMCP-enabled page and click the extension’s toolbar icon to open the side panel.
Clicking the toolbar icon is what grants the extension access to the current site, so click it again after you switch to another site. Chrome internal pages and the Chrome Web Store cannot be inspected.

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Inspect and call tools

With the panel open, the tool list shows each tool the page registered with its description and parameter count, and a search box to filter them. Select a tool to get a form generated from its schema, fill it in, and run it with Execute (or Cmd/Ctrl + Enter). The panel validates input against the tool’s JSON Schema before execution, and offers a raw JSON mode when a form is awkward for nested inputs. Results are shown with timing and errors, in a split you can drag or expand to fullscreen. Requests you want to keep can be saved by name; saved requests are stored locally and scoped to the site’s origin. The list refreshes automatically when the page registers or removes tools, when you change tabs, and on page loads.

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Build from source

Use Node 22.12+ and pnpm.
Then load .output/chrome-mv3 unpacked, following the same chrome://extensions steps as above. For iterating on the extension itself, pnpm dev runs a WXT development build with hot reload; load .output/chrome-mv3-dev instead. pnpm zip produces a release zip in .output.

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Next steps

mcp-use Inspector

Debug a remote or local MCP server from the browser: tools, resources, prompts, chat, and widgets.

Chrome WebMCP docs

The imperative WebMCP API a page uses to register the tools this extension inspects.