To disconnect, open QuickBooks Online → Apps → My Apps and disconnect this app.
Then, on the operator's machine, remove the stored credentials:
security delete-generic-password -s qbo-refresh-token,
security delete-generic-password -s qbo-realm-id, and delete
QUICKBOOKS_REFRESH_TOKEN / QUICKBOOKS_REALM_ID from the MCP server's .env.
Nothing is stored anywhere else.