DOCSP-19047 Add generic message command syntax example

Author: ianf-mongodb

source/reference/command.txt

@@ -21,15 +21,30 @@ To run a command against the current database, use :method:`db.runCommand()`:
 
 .. code-block:: javascript
 
-   db.runCommand( { <command> } )
+   db.runCommand( { <command> } );
 
 To run an administrative command against the ``admin`` database, use :method:`db.adminCommand()`:
 
 .. code-block:: javascript
 
-   db.adminCommand( { <command> } )
+   db.adminCommand( { <command> } );
 
-.. include:: /includes/extracts/commands-toc-explanation.rst
+.. note::
+
+   For details on specific commands, including syntax and examples, 
+   click on the specific command to go to its reference page.
+
+Command Syntax
+--------------
+
+When you run a database command, you specify the command as a document 
+to :method:`db.runCommand()`. The document's key is the command to run,
+and the value is typically supplied as ``1``. The value does not affect
+the output of the command for example:
+
+.. code-block:: javascript
+
+  db.runCommand( { hello: 1 } );
 
 User Commands
 -------------