expense-tracker-mcp-server

The server uses environment variables (`MONGODB_URI`) for sensitive connection strings, indicating good practice against hardcoded secrets. MongoDB connections are configured with TLS and certificate verification (`tls=True`, `tlsCAFile=certifi.where()`). Authentication and authorization logic (`is_user_in_group`, `is_user_group_admin`, etc.) are heavily integrated into the tools, requiring `user_id` for most operations. Input validation is present for critical parameters like group names, amounts, and email formats. There are no obvious `eval` or other dangerous dynamic code execution patterns. The MongoDB schema `additionalProperties: True` allows for flexible document structure but could be made stricter for enhanced data integrity if desired, though this is not a direct security vulnerability.