WebMCP support now available in mcp-handler
By Steven Van ·
mcp-handler 2.2.0 lets sites expose an allowlisted set of MCP tools to in-page agents via one script tag, authenticated as the signed-in user.
Vercel's mcp-handler now has experimental support for WebMCP, a proposed web standard for exposing tools to in-browser agents. A single script tag on a site makes its existing MCP tools available to in-page agents as well.
Tools are opted in one by one through an experimental_webMcp allowlist on the handler; only listed tools are exposed to the page. The script loads from the MCP endpoint with a ?webmcp-script parameter, registers the allowlisted tools with the page, and proxies each call back to the MCP server as the signed-in user, so authenticated tools work without a browser-side OAuth flow.
The feature ships in mcp-handler 2.2.0. Setup details are in the WebMCP documentation.