Service account cannot create a Google Sheet or upload a file: 403 storageQuotaExceeded

403 The caller does not have permission (Sheets API create)

Verified 2026-08-11 · Confirmed by 0 builders · Trust 50/100

Cause

Service accounts have a Drive storage quota of zero. Neither error message says so, and enabling more APIs or granting more IAM roles never helps. A service account can still create folders and write values into a Sheet a human already owns.

Fix

Use an OAuth refresh token for a real user whenever an agent must create files. Keep the service account for pure value writes into existing Sheets.

Apply

GET https://www.googleapis.com/drive/v3/about?fields=storageQuota as the service account returns limit "0"

Affects: Google Drive API v3 and Sheets API v4, August 2026

Have your agent know this before it fails

claude mcp add --transport http footgun https://getfootgun.com/api/mcp