Smartsheet is a Caddi-managed connector. There is no Smartsheet app registration to create and nothing for an administrator to configure — you sign in to Smartsheet and approve Caddi.
Before you start
You'll need:
A Smartsheet account with access to the sheets and workspaces the work involves
A Caddi account
Step 1: Connect your account
In Caddi, open Settings, then Integrations, and go to the My Connections tab.
Find Smartsheet and click Connect +.
Sign in to Smartsheet.
Review the permissions on the authorization screen and click Allow.
You'll be returned to Caddi with the connection active.
How the connection behaves
Caddi inherits your Smartsheet permissions, exactly. The connection acts as you, so it reaches the sheets shared with you at the access level you already have. A loop that fails to edit a sheet usually means your own access to that sheet is Viewer or Editor-without-share.
Creating sheets requires a licensed user. Smartsheet restricts sheet creation to licensed users, so the connected account needs a Smartsheet licence to create sheets.
Permissions are chosen at sign-in. Smartsheet lists them on the authorization screen — read them there.
Tokens renew in the background, so you should not need to reconnect.
Each person connects their own Smartsheet account.
Troubleshooting
A sheet or workspace is invisible to Caddi
It is not shared with your Smartsheet account. Have the owner share it with you in Smartsheet.
Changes to a sheet fail
Either your access to that sheet is Viewer, or only read permissions were granted at sign-in. Check the sharing level in Smartsheet first, then disconnect and reconnect to re-approve.
Creating a new sheet fails
The connected Smartsheet user is not a licensed sheet creator. Ask your Smartsheet administrator for a licence.
Still stuck? Contact Caddi support with the exact error message you're seeing and the time it occurred.
Sources
OAuth and access tokens — Smartsheet API reference