[md]stdio

mcp-stdio · JVM · Scala.js · Scala Native

stdin/stdout JSON-RPC transport for subprocess-based MCP servers — the format expected by Claude Desktop and Claude Code's local server config. A server built with core becomes a stdio server by handing it to StdioTransport.run.

libraryDependencies += "net.andimiller.mcp" %%% "mcp-stdio" % "0.10.0"

StdioTransport.run reads JSON-RPC from stdin, dispatches it to your Server[F], and writes responses back to stdout. The whole serve loop is one line:

import cats.effect.{IO, IOApp}
import net.andimiller.mcp.core.server.{Server, ServerBuilder}
import net.andimiller.mcp.stdio.StdioTransport

object MyServer extends IOApp.Simple:
  def server: IO[Server[IO]] =
    ServerBuilder[IO]("my-server", "1.0.0").build

  def run: IO[Unit] = server.flatMap(StdioTransport.run[IO])

See Server construction → Stdio server for the server side, or Clients → Client construction for spawning a subprocess server as an McpClient.