Error format

All API errors are JSON with an error string and optional details.

{
  "error": "invalid_token"
}

Common HTTP status codes

• 400 – validation error
• 401 – invalid client/token
• 403 – insufficient scope
• 404 – not found
• 415 – unsupported media type (non-PDF)
• 500 – server error

Notes

• signed_download.php returns 403 if the contract is not fully signed.
• Invitation sending uses mail() in this add-on. If you need SMTP/Resend/SendGrid, adapt api_send_mail() only.