Runs npm and Python packages in Docker; additional layer of security for MCP servers

mcpc

#!/bin/sh
# mcpc - MCP Container wrapper for uvx/npx runtimes

set -e

if [ $# -lt 2 ]; then
    printf "Usage: mcpc {uv|uvx|npx} [options] <package> [args...]\n" >&2
    printf "\nOptions:\n" >&2
    printf "  --python-version=X.Y    Python version for uvx (default: 3.13)\n" >&2
    printf "  --node-version=X        Node version for npx (default: 22)\n" >&2
    exit 1
fi

runtime="$1"
shift

# Default versions
python_version="3.13"
node_version="22"

# Parse version flags
while [ $# -gt 0 ]; do
    case "$1" in
        --python-version=*)
            python_version="${1#--python-version=}"
            shift
            ;;
        --python-version)
            python_version="$2"
            shift 2
            ;;
        --node-version=*)
            node_version="${1#--node-version=}"
            shift
            ;;
        --node-version)
            node_version="$2"
            shift 2
            ;;
        *)
            # Not a flag, must be the package name
            break
            ;;
    esac
done

if [ $# -eq 0 ]; then
    printf "Error: No package specified\n" >&2
    exit 1
fi

# Detect if stdin is a TTY for proper terminal handling
if [ -t 0 ]; then
    tty_flag="-t"
else
    tty_flag=""
fi

case "$runtime" in
    uv|uvx)
        image="ghcr.io/astral-sh/uv:python${python_version}-alpine"
        cache_volume="uv-cache"
        cache_dir="/mnt/cache"
        cache_env="UV_CACHE_DIR=${cache_dir}"
        ;;

    npx)
        image="node:${node_version}-alpine"
        cache_volume="npm-cache-${node_version}"
        cache_dir="/mnt/cache"
        cache_env="NPM_CONFIG_CACHE=${cache_dir}"
        ;;

    *)
        printf "Error: Unknown runtime '%s'. Supported: uvx, npx\n" "$runtime" >&2
        exit 1
        ;;
esac

exec docker run \
    --rm \
    -i $tty_flag \
    -v "${cache_volume}:${cache_dir}" \
    -e "${cache_env}" \
    -w "/workspace" \
    "${image}" \
    "${runtime}" \
    "$@"

Example:

  "mcpServers": {
    "semantic-scholar": {
      "command": "mcpc",
      "args": ["uvx", "semantic-scholar-mcp"]
    }
  }