mcp 0.5.0 - path traversal via tool params works with zero sanitization

1. Tested with tool param `../../etc/passwd` on filesystem read tool 2. SDK passes it straight through, tool resolves full path and returns file contents 3. No validation, no chroot, no path canonicalization Tested on mcp 0.5.0, linux 5.15. Tool implementers are expected to sanitize manually but there's zero guidance in docs about what attacks to defend against.