-This macro defines a new Lisp data type called NAME, which contains data
-stored in SLOTs. This defines a `make-NAME' constructor, a `copy-NAME'
-copier, a `NAME-p' predicate, and setf-able `NAME-SLOT' accessors.
+This macro defines a new data type called NAME that stores data
+in SLOTs. It defines a `make-NAME' constructor, a `copy-NAME'
+copier, a `NAME-p' predicate, and slot accessors named `NAME-SLOT'.
+You can use the accessors to set the corresponding slots, via `setf'.
+
+NAME may instead take the form (NAME OPTIONS...), where each
+OPTION is either a single keyword or (KEYWORD VALUE).
+See Info node `(cl)Structures' for a list of valid keywords.
+
+Each SLOT may instead take the form (SLOT SLOT-OPTS...), where
+SLOT-OPTS are keyword-value pairs for that slot. Currently, only
+one keyword is supported, `:read-only'. If this has a non-nil
+value, that slot cannot be set via `setf'.