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WebMCP support now available in mcp-handler

mcp-handler 2.2.0 can expose selected MCP tools to in-browser agents through one script, proxying calls as the signed-in user without separate browser OAuth.

Vercel · Sep 18, 2026
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Source Summary

**mcp-handler 2.2.0** adds experimental **WebMCP** support. Developers opt tools into experimental_webMcp, then load a script from the MCP endpoint with the webmcp-script query parameter.

Practical Implication

If you already maintain MCP tools, this offers a short path to reuse selected ones inside browser agents. The generated script registers them on the page and proxies calls to the existing server as the signed-in user.

Agent-Ready Context
**mcp-handler 2.2.0** adds experimental **WebMCP** support. Developers opt tools into experimental_webMcp, then load a script from the MCP endpoint with the webmcp-script query parameter.

If you already maintain MCP tools, this offers a short path to reuse selected ones inside browser agents. The generated script registers them on the page and proxies calls to the existing server as the signed-in user.

WebMCP remains a proposed standard and this integration is explicitly experimental. Tool exposure should therefore be narrow, with authentication and authorization checked at the server boundary.
Connected Context · Feed7 Judgment

This creates a direct reuse path from existing MCP servers into browser agents, reducing the need to rebuild selected tools for page contexts. Against the candidates, it advances discoverability beyond passive agent instructions but introduces a sharper authority boundary: calls execute through the existing server as the signed-in user. Because both WebMCP and the integration are experimental, narrow exposure and server-side authorization remain implementation requirements.

Rebuilding the web for agents — Liad Yosef, MCP AppsWebMCP provides the callable, discoverable interface that the observed failure of passive llms.txt instructions suggests agent-ready sites need.Latest MCP spec now supported in mcp-handlerThe earlier mcp-handler upgrade defines runtime and protocol prerequisites that existing deployments may need to satisfy before adopting this newer browser-facing capability.ChromeDevTools/chrome-devtools-mcpChrome DevTools MCP gives agents browser control from an external tool server, whereas WebMCP exposes selected site-owned tools on the page; together they clarify complementary automation and application-action surfaces.MCP Apps: Extending the Frontier — Ido Salomon & Liad YosefMCP Apps returns sandboxed interfaces under host control, while WebMCP registers page tools that proxy authenticated server calls, making authorization more central than UI rendering.
Context Map
contextcoding#mcp#tool-use
Uncertainty
WebMCP remains a proposed standard and this integration is explicitly experimental. Tool exposure should therefore be narrow, with authentication and authorization checked at the server boundary.