--- a/runtime/doc/tagsrch.txt
+++ b/runtime/doc/tagsrch.txt
@@ -888,19 +888,25 @@ like |CTRL-]|.
 
 The function used for generating the taglist is specified by setting the
 'tagfunc' option.  The function will be called with three arguments:
-   a:pattern	The tag identifier used during the tag search.
-   a:flags	List of flags to control the function behavior.
+   a:pattern	The tag identifier or pattern used during the tag search.
+   a:flags	String containing flags to control the function behavior.
    a:info	Dict containing the following entries:
 		    buf_ffname	  Full filename which can be used for priority.
 		    user_data	  Custom data String, if stored in the tag
 				  stack previously by tagfunc.
 
-Currently two flags may be passed to the tag function:
+Currently up to three flags may be passed to the tag function:
   'c'		The function was invoked by a normal command being processed
 	        (mnemonic: the tag function may use the context around the
 		cursor to perform a better job of generating the tag list.)
   'i'		In Insert mode, the user was completing a tag (with
-		|i_CTRL-X_CTRL-]|).
+		|i_CTRL-X_CTRL-]| or 'completeopt' contains `t`).
+  'r'		The first argument to tagfunc should be interpreted as a
+		|pattern| (see |tag-regexp|), such as when using: >
+		  :tag /pat
+<		It is also given when completing in insert mode.
+		If this flag is not present, the argument is usually taken
+		literally as the full tag name.
 
 Note that when 'tagfunc' is set, the priority of the tags described in
 |tag-priority| does not apply.  Instead, the priority is exactly as the