Most MCP servers in the registry are stdio-based packages meant for local use. Here's how to expose them over HTTP so you can test them in MCP Playground.
MCP Playground connects to remote servers over HTTP (Streamable HTTP or SSE transport). Stdio-based servers communicate through standard input/output and need a local process to bridge them to HTTP. This is by design — running arbitrary processes in the browser would be a security risk.
supergateway wraps any stdio MCP server and exposes it as an SSE endpoint with one command.
Install globally
npm install -g supergatewayRun any stdio server over SSE (example: filesystem server)
npx supergateway --stdio 'npx -y @modelcontextprotocol/server-filesystem /tmp' --port 3001Then connect in MCP Playground
http://localhost:3001/ssemcp-proxy is a Python tool that bridges stdio servers to SSE.
Install
pip install mcp-proxyRun a server with SSE transport
mcp-proxy --sse-port 3001 -- npx -y @modelcontextprotocol/server-filesystem /tmpSome servers already support HTTP transport natively. Check the server's README for flags like --transport sse or --transport http.
Example: a server with built-in SSE support
npx -y some-mcp-server --transport sse --port 3001pnpm test-server in this repo.