Trello uses OAuth 1.0a and issues API credentials through a Power-Up in the Trello admin portal. You have to create a Power-Up first even if you only want API credentials — Atlassian no longer issues keys any other way.
The old trello.com/app-key page has been retired in favour of the Power-Up admin portal at trello.com/apps/admin. If you hold a legacy key from the old page, there is no automatic migration — create a new key under a Power-Up and have users reconnect.
Before you start
You'll need:
Workspace admin on the Trello Workspace that will own the Power-Up
Owner or Admin access to your Caddi organization
The free Trello plan is sufficient, and Atlassian approval is not required — listing a Power-Up in the directory is a separate process you don't need here.
Step 1: Create a Power-Up to hold the API key
Atlassian requires a Power-Up before it will issue an API key. You are not shipping a Power-Up — this is just the container for the credentials.
Go to trello.com/apps/admin.
Click Create New Power-Up.
Name —
CaddiTeam / Workspace — select the workspace that should own it.
iframe Connector URL — this field is required.
https://trycaddi.comis a fine placeholder since the Power-Up itself is never used.On the Basic Information form, fill in Email, Support Email, and Author.
Save.
Step 2: Generate the API key and secret
Open the Power-Up you just created and go to the API Key tab.
Click Generate a new API Key.
Copy the API Key.
On the same tab, reveal and copy the Secret — Trello also calls this the OAuth Secret.
In OAuth 1.0a terms, the API Key is your consumer key and the Secret is your consumer secret. Trello notes that the API key itself is not sensitive; the Secret is.
Step 3: Configure Trello in Caddi
This step must be completed by a Caddi organization owner or admin.
In Caddi, open Integrations in the left sidebar, then click the Integration Setup tab at the top of the page. This tab is only visible to organization owners and admins.
Find Trello in the list and click Configure.
Enter the following values:
API Key — the API Key from the Power-Up's API Key tab
OAuth Secret — the Secret from the same tab
Permissions — comma-separated. Enter
read,writefor full read and write access. Addaccountonly if a loop needs the user's email address — that's the closest thing Trello has to an elevated scope.Token Expiration — choose never. Trello OAuth 1.0a has no refresh token, so any other value forces users to re-authorize when it lapses.
Application Name — the name shown to users during authorization.
Caddiis a sensible value.
Click Save Configuration. Caddi validates the credentials immediately — if something is wrong you'll see an error right away, and nothing is stored until validation passes.
Step 4: Connect your account
Go back to the My Connections tab and find Trello.
Click Connect + and sign in to Trello.
Approve the requested permissions. You'll be returned to Caddi with the connection active.
How the connection behaves
Each user connects their own Trello account. Caddi sees the boards that user can see.
There is no redirect URI to register. Trello's OAuth 1.0a flow supplies the callback at request time, so nothing needs configuring in the Power-Up for it.
Token expiration is set by you, and there is no refresh. With never selected, connections stay live until revoked. With anything shorter, users will have to re-authorize when the token lapses.
Rate limits are shared across your key. Trello allows 300 requests per 10 seconds per API key and 100 per 10 seconds per token, with
/members/endpoints further capped at 100 per 15 minutes. The per-key ceiling is shared by everyone in your organization.Revoking access. Generate a new API Key on the Power-Up, or have users revoke Caddi from their Trello account settings under Applications.
Troubleshooting
There's no way to generate an API key
You need to create a Power-Up first — Atlassian only issues keys under one. See Step 1.
Users are asked to reconnect after a day or a month
Token Expiration is set to something other than never. Change it, then have users reconnect once.
The connection works but Caddi can't modify cards
Permissions is set to read only. Change it to read,write and have users reconnect.
Rate-limit errors when several people run loops at once
The 300-per-10-seconds per-key ceiling is shared. Stagger scheduled loops.
Still stuck? Contact Caddi support with the exact error message you're seeing and the time it occurred.
Automation ideas
Law Firms
New matter → board and card set
Caddi creates the matter's Trello cards from your template list, assigns members, and sets due dates from the matter's deadlines.
Card moved → matter status update
When a card moves list, Caddi updates the matter status in your practice management system and logs the change.
RIAs
Onboarding → tracked checklist
Caddi creates the client onboarding cards, one per outstanding document, and closes them as items arrive.