--- a/doc/gutentags.txt	Fri Sep 16 23:43:57 2016 +0800
+++ b/doc/gutentags.txt	Sat Oct 29 01:11:02 2016 +0800
@@ -59,8 +59,29 @@
 always consistent with the source code.
 
 Also, Gutentags is clever enough to not stumble upon itself by triggering
-multiple ctags processes if you save files too fast, or your project is really
-big.
+multiple ctags processes if you save files too fast, or if your project is
+really big.
+
+
+1.1 Requirements
+                                                *gutentags-ctags-requirements*
+
+If you're using the `ctags` modules (which is the default and only working one
+at this point, really), you will need a `tags` generator that supports the
+following arguments:
+
+* `-f` (to specify the output file)
+* `--append` (to append to an existing file while keeping it sorted)
+* `--exclude` (to exclude file patterns)
+* `--options` (to specify an options file)
+
+This means you probably want Exhuberant Ctags or Universal Ctags. The basic
+old BSD Ctags WON'T WORK. Other language-specific versions may or may not
+work. Check with their help or man page.
+
+
+1.2 Similar Plugins
+                                                *gutentags-similar-plugins*
 
 There are some similar Vim plugins out there ("vim-tags", "vim-autotag",
 "vim-automatic-ctags", etc.). They all fail on one or more of the requirements
@@ -87,7 +108,7 @@
 The following commands are only available in buffers that have been found to
 belong to a project that should be managed by Gutentags. See
 |gutentags_project_root| for how Gutentags figures out the project a file
-belongs to. When not project is found (i.e. the file is not under any of the
+belongs to. When no project is found (i.e. the file is not under any of the
 known project markers), Gutentags is disabled for that buffer, and the
 following commands and remarks don't apply.
 
@@ -216,8 +237,9 @@
                         Specifies the ctags executable to launch for a project
                         of type {type}. See |gutentags_project_info| for more
                         information.
+                        IMPORTANT: piease see |gutentags-ctags-requirements|.
                         Example: >
-                         let g:gutentags_ctags_executable_ruby = 'ripper-tags'
+                         let g:gutentags_ctags_executable_ruby = 'foobar'
 <
 
                                                 *gutentags_tagfile*