Using a formula to append strings

[Vitalii]

No idea, why my every attempt to paste data via the API fails.

Now, I try to paste the complex string to the column of type "long string".
Data sample: 

["https://app.clickup.com/t/123","https://app.clickup.com/t/456"]

When I paste it manually, it works fine and I see in the airtable.
But when I push this data via the API, I get an error

ERROR: Your request is invalid or could not be processed by the service
Cannot parse value "["https://app.clickup.com/t/123","https://app.clickup.com/t/456"]" for field tasks

PS: the same data goes to the google spreadsheet just fine.

[Vitalii · Accepted solution]

.toString() helped me to transform the list to the proper string