diff --git a/funcs/func_cdr.c b/funcs/func_cdr.c
index 039e45ca75e49fe5bae434c01a794b0096e4d0b3..c868af17cd3005c8dbba3bd91945d605fe40158d 100644
--- a/funcs/func_cdr.c
+++ b/funcs/func_cdr.c
@@ -130,6 +130,18 @@ static struct ast_custom_function cdr_function = {
 "  values, when the 'u' option is passed, but formatted as YYYY-MM-DD HH:MM:SS\n"
 "  otherwise.  Similarly, disposition and amaflags will return their raw\n"
 "  integral values.\n",
+"  Here is a list of all the available cdr field names:\n",
+"    clid          lastdata       disposition\n"
+"    src           start          amaflags\n"
+"    dst           answer         accountcode\n"
+"    dcontext      end            uniqueid\n"
+"    dstchannel    duration       userfield\n"
+"    lastapp       billsec        channel\n"
+"  All of the above variables are read-only, except for accountcode,\n"
+"  userfield, and amaflags. You may, however,  supply\n"
+"  a name not on the above list, and create your own\n"
+"  variable, whose value can be changed with this function,\n"
+"  and this variable will be stored on the cdr.\n",
 };
 
 static int unload_module(void)