docs: update api/description/builtin-rules.md (#256)

Author: qudix

docs/api/description/builtin-rules.md

@@ -468,7 +468,7 @@ For more information on WDK rules, see: [#159](https://github.com/xmake-io/xmake
 
 ## plugin.vsxmake.autoupdate
 
-We can use this rule to automatically update the VS project file (when each build is completed) in the VS project generated by `xmake project -k vsxmake`.
+Automatically update the VS project file (when each build is completed) in the VS project generated by `xmake project -k vsxmake`.
 
 ```lua
 add_rules("plugin.vsxmake.autoupdate")
@@ -479,10 +479,21 @@ target("test")
 
 ## plugin.compile_commands.autoupdate
 
-We can also use this rule to automatically update the generated `compile_commands.json`
+Automatically update the `compile_commands.json` file, commonly used with language servers like clangd:
+
+```lua
+add_rules("plugin.compile_commands.autoupdate")
+
+target("test")
+    set_kind("binary")
+    add_files("src/*.c")
+```
+
+And if needed, set a custom output directory:
 
 ```lua
 add_rules("plugin.compile_commands.autoupdate", {outputdir = ".vscode"})
+
 target("test")
     set_kind("binary")
     add_files("src/*.c")