# Webmcp Extension > DevTools for the agentic web — detect, inspect, and test WebMCP tools in Chrome - **Type:** MCP server - **Install:** `agentstack add mcp-amrinbuilds-webmcp-extension` - **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior - **Seller:** [amrinbuilds](https://agentstack.voostack.com/s/amrinbuilds) - **Installs:** 0 - **Category:** [Web & Browser](https://agentstack.voostack.com/c/web-and-browser) - **Latest version:** 0.1.0 - **License:** MIT - **Upstream author:** [amrinbuilds](https://github.com/amrinbuilds) - **Source:** https://github.com/amrinbuilds/webmcp-extension ## Install ```sh agentstack add mcp-amrinbuilds-webmcp-extension ``` Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent. ## About # WebMCP Scout **DevTools for the agentic web.** WebMCP Scout is a Chrome extension that detects, visualizes, and tests [WebMCP](https://github.com/webmachinelearning/webmcp) tools registered on any web page — and audits HTML forms for agent-readiness via the WebMCP Declarative API. Built during Chrome's WebMCP Early Preview Program (Chrome 146+). --- ## What is WebMCP? WebMCP is a proposed web standard that lets websites expose structured tools to in-browser AI agents — replacing fragile screen-scraping with robust, schema-driven tool invocation. Think of it as MCP, but native to the browser. - **Imperative API**: Register tools via `navigator.modelContext.registerTool()` - **Declarative API**: Annotate HTML `` elements with `toolname` and `tooldescription` attributes WebMCP Scout gives you visibility into both. --- ## Features - **Tool Detection** — Detects imperative and declarative WebMCP tools registered on the active tab in real time - **Schema Visualization** — Displays full JSON Schema definitions for every registered tool - **Manual Execution** — Execute tools directly with custom input arguments, bypassing the LLM layer for deterministic testing - **Form Scanner** — Audits HTML forms for WebMCP Declarative API compatibility, surfacing agent-readiness gaps and annotation opportunities - **Overlap Filtering** — Filters forms already covered by imperative tools to eliminate false positives - **Sensitive Field Detection** — Identifies password, payment, and PII fields with inline safety warnings - **Live Badge** — Real-time badge showing tool count (green) and scannable form count (red) --- ## Requirements - Chrome 146.0.7672.0 or higher - WebMCP flag enabled ### Enable the WebMCP flag 1. Open Chrome and navigate to `chrome://flags/#enable-webmcp-testing` 2. Set the flag to **Enabled** 3. Relaunch Chrome --- ## Installation WebMCP Scout is not yet on the Chrome Web Store. To install manually: 1. Clone or download this repo 2. Open Chrome and navigate to `chrome://extensions` 3. Enable **Developer mode** (top right toggle) 4. Click **Load unpacked** 5. Select the repo folder The Scout icon will appear in your toolbar. Navigate to any page with WebMCP tools registered and click the icon to open the side panel. --- ## Usage ### Tools Tab Shows all WebMCP tools detected on the current page — name, description, and full input schema. Click any tool to expand and execute it manually with custom JSON arguments. ### Scan Tab Audits all `` elements on the page for WebMCP Declarative API compatibility. For each form, Scout shows: - Suggested `toolname` and `tooldescription` values - Inferred JSON Schema for form fields - Sensitive field warnings - Missing annotation flags Forms already covered by registered imperative tools are filtered out automatically. --- ## Background WebMCP Scout was built as a hands-on exploration of the WebMCP Early Preview Program. As AI agents move from screen-scraping to structured tool invocation, developers need observability tooling to build and debug agent-ready web experiences. This extension is part of broader work at the intersection of agentic SEO, AI agent infrastructure, and emerging web standards. Learn more at [amrin.dev](https://amrin.dev) --- ## WebMCP Resources - [WebMCP Early Preview Docs](https://developer.chrome.com/docs/extensions/ai/webmcp) - [WebMCP GitHub Spec](https://github.com/webmachinelearning/webmcp) - [Chrome Labs Demos](https://googlechromelabs.github.io/webmcp-tools/) - [Chrome AI Dev Preview Discussion Group](https://groups.google.com/a/chromium.org/g/chrome-ai-dev-preview-discuss/) --- ## Status Early preview / active development. Built against the March 2026 WebMCP spec. Notable spec changes tracked: - `toolparamtitle` removed (Mar 12, 2026) - `provideContext` / `clearContext` removed (Mar 6, 2026) --- ## License MIT — see [LICENSE](./LICENSE) --- ## Contributing Issues and PRs welcome. If you find a page where Scout misbehaves or misses tools, please open an issue with the URL and a description of what you expected. ## Source & license This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code. - **Author:** [amrinbuilds](https://github.com/amrinbuilds) - **Source:** [amrinbuilds/webmcp-extension](https://github.com/amrinbuilds/webmcp-extension) - **License:** MIT Install and usage instructions live in the source repository linked above. ## Pricing - **Free** — Free ## Security capabilities Automated source analysis of v0.1.0 — what this tool can access: - **Network access:** no - **Filesystem access:** no - **Shell / process execution:** no - **Environment & secrets:** no - **Dynamic code execution:** no *"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.* ## Versions - **0.1.0** — security scan: passed — Imported from the upstream source. ## Links - Listing page: https://agentstack.voostack.com/l/mcp-amrinbuilds-webmcp-extension - Seller: https://agentstack.voostack.com/s/amrinbuilds - Browse the marketplace: https://agentstack.voostack.com/browse --- Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.