How do roots provide security boundaries for MCP servers?

Roots limit file access to only the directories the user has explicitly approved. If you grant access only to your Desktop folder, the MCP server cannot access files in Documents, Downloads, or any other location. When Claude tries to access a file outside the approved roots, it receives an error and can inform the user that the file is not accessible from the current server configuration. This prevents accidental access to sensitive files and gives users granular control over what each MCP server can see and interact with on their system.