sample mcp server in shell

AAAREADME.md

A sample server that says something... it works on MacOS. It needs to be adapted to work on other OS.

This is simply a tool to demonstrate how MCP works with JSON-RPC

testMCPServer.sh

#!/bin/zsh

initialize() {
  local id=$(jq -r '.id' <<< "$current_json")
  echo '{"jsonrpc":"2.0","id":'${id}',"result":{"protocolVersion":"2024-11-05","capabilities":{"tools":{}},"serverInfo":{"name":"mcpSampleShell","version":"1.0.0"}}}'
}


tool_list() {
  local id=$(jq -r '.id' <<< "$current_json")
  echo '{"jsonrpc":"2.0","id":'${id}',"result":{"tools":[{"description":"say out loud a text","inputSchema":{"type":"object","properties":{"text":{"description":"The text to say","type":"string"}},"required":["text"]},"name":"say"}]}}'
}

void() {
  local id=$(jq -r '.id' <<< "$current_json")
  echo '{"jsonrpc":"2.0","id":'${id}',"result":{}}'
}

tool_call() {
  # Ensure the name is cURL

  if jq -e '.params.name == "say"' <<< "$current_json" > /dev/null; then
    local id=$(jq -r '.id' <<< "$current_json")
    text=$(jq -r '.params.arguments.text' <<< "$current_json")

    /usr/bin/say -v "Alex" $text -o /tmp/temp.aiff && /usr/bin/afplay /tmp/temp.aiff && rm /tmp/temp.aiff
    echo   '{"jsonrpc":"2.0","id":'${id}',"result":{"content":[{"type":"text","text":"success"} ] } }'
    echo   '{"jsonrpc":"2.0","id":'${id}',"result":{"content":[{"type":"text","text":"success"} ] } }' >> /tmp/call
  fi
}


current_json=""
while read line; do
  current_json=${current_json}${line}
  # Check if this is a valid json
  echo ${current_json} | jq . 2>/dev/null >/dev/null || continue

  if ! jq -e '.jsonrpc == "2.0"' <<< "$current_json" > /dev/null; then
    echo "bad jsonrpc call ${current_json}" >&2
    current_json=""
    continue
  fi
  echo $current_json >> /tmp/call

  method=$(jq -r '.method' <<< "$current_json")
  case "$method" in
    "initialize")
      initialize
      ;;
    "tools/list")
      tool_list
      ;;
    "tools/call")
      tool_call
      ;;
    "resources/templates/list")
      void
      ;;
    *)
      void
      echo "Unknown method: $method" >> /tmp/call
      ;;
  esac


  current_json=""
done