Add to user tools guide

docs/ADD_DOCUMENTATION.md

@@ -0,0 +1,14 @@
+# Add Documentation Tool
+The `add_docs` tool scans the PR code changes, and automatically suggests documentation for the undocumented code components (functions, classes, etc.).
+
+It can be invoked manually by commenting on any PR:
+```
+/add_docs
+```
+For example:
+<kbd><img src=./../pics/add_docs_comment.png width="768"></kbd>
+<kbd><img src=./../pics/add_docs.png width="768"></kbd>
+
+### Configuration options
+ - `docs_style`: The exact style of the documentation (for python docstring). you can choose between: `google`, `numpy`, `sphinx`, `restructuredtext`, `plain`. Default is `sphinx`.
+ - `extra_instructions`: Optional extra instructions to the tool. For example: "focus on the changes in the file X. Ignore change in ...".

docs/TOOLS_GUIDE.md

@@ -5,5 +5,6 @@
 - [ASK](./ASK.md)
 - [SIMILAR_ISSUE](./SIMILAR_ISSUE.md)
 - [UPDATE CHANGELOG](./UPDATE_CHANGELOG.md)
+- [ADD DOCUMENTATION](./ADD_DOCUMENTATION.md)
 
 See the **[installation guide](/INSTALL.md)** for instructions on how to setup PR-Agent.