Basecamp 3 - can't Get Message ID to read message content

What am I trying to achieve
We are organising events in our company on a regular basis. When a new event to-do list is created in Basecamp 3, a task named EVENT INFO is also created where a user adds information about the event and then marks the task as completed. Then the automation will send the comment info to ChatGPT to output various content types, create a ticket buying event page in our ticket tool and create a newsletter to send out to people.

What have I done so far
My thought process is that I will Make watch for To-Do completions in BS3 (as I havent figured out a way to do a finer/better trigger) → then I will filter those To-Dos containing a specific keyword (EVENT INFO that has been preprogramed into the BS3 template) → via BS3: get a message get the info about the event and send it to ChatGPT.

Where am I stuck
BS3: Get a message requires a parameter “Message ID” which I have not been able to identify amongst the outputs of BS3: Watch a to-do completion. Nor have I found another module that would get info. I have tried mapping parameters Recording_ID, Recording_URL and Recording_APP_URL to no avail and there is nothing like Message_ID in the outputs.

Any idea how to tackle this please?

Thank you kindly!