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mcp-handler 2.2.0 exposes existing MCP tools to in-browser agents with one script tag
Vercel shipped experimental WebMCP support in mcp-handler 2.2.0 on 18 September. Tools opt in through an experimental_webMcp config object, a script tag loads the handler with a ?webmcp-script parameter, and each call proxies back to the MCP server as the signed-in user, so authenticated tools work without a browser-side OAuth flow. That last detail is the interesting one: it removes the main reason browser-resident agents could not reach authenticated server tools.
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