Edit custom field via REST


I have a server with a custom field, specifically “is-spam”. How do I
address this field for editing via the REST interface.

Setting the standard fields works fine for me.

I’ve been sending stuff like: “content=is-spam: yes” and
"content=CF-is-spam: yes" but I always get something like:

… 409 Syntax Error

cf-is-spam: Unknown field.

CF-is-spam: yes

Any help much appreciated.

“Cut your own wood and it will warm you twice”