API calls are not asset class specific.
When you want to find a specific data field, you should check the Data Content Guide (the latest one is available here.). Open tab "Field Descriptions", and use a text filter on column D or E to display only the rows that "contain" a keyword that defines what you are looking for, in this case "Dividend". You will find that Dividends are available in several templates, not only Corax. I guess what you need is a "Terms & Conditions" request, field "Latest Dividend":
It delivers a fund's most recent dividend amount, and coverage is available for Mutual Funds as can be seen in column AA (see a more detailed explanation on coverage below).
Checking coverage by asset class, example for Corax & Mutual Funds
This is a side note, just to give you a more complete view.
In DSS Corporate Actions data is currently only available for Equity. There is no coverage for other asset classes, including Mutual Funds.
Data coverage is also in the Data Content Guide. Scroll to the right to see the data coverage by asset class in columns O to AH. You will find Mutual Funds in column AA, and we see that for Corax the cells contain "n", which means "no coverage":