@agiletortoise Thanks for this.
Airtable’s documentation states that:
Airtable API performs automatic data conversion from string values if typecast parameter is passed in. Automatic conversion is disabled by default to ensure data integrity, but it may be helpful for integrating with 3rd party data sources.
When the parameter is inserted where I have it in the script, then the script will execute; however, the contents of the tags field are ignored. If I remove the parameter entirely then I get a 422: Invalid Request error and the script fails. The API needs the data to be entered into a multiselect field to be formatted, e.g. item1,item2,item3. The two possible solutions I have identified are: remove the trailing comma from the output in Drafts, or use the typecast parameter to get the API to tidy things up. I suppose a third alternative would be to forget the multiselect prompt and just go with a simple text box, but this would be less user-friendly and the available tags would not be visible at the prompt.