Update text after review

Author: xuniq

doc/reference/reference_lua/box_info.rst

@@ -28,11 +28,13 @@ variables.
 * **pid** is the process ID. This value is also shown by
   :ref:`tarantool <tarantool-build>` module
   and by the Linux command ``ps -A``.
-* **ro** is ``true`` if the instance is in "read-only" mode
+* **ro** is ``true`` if the instance is in read-only mode
   (same as :ref:`read_only <cfg_basic-read_only>` in ``box.cfg{}``),
   or if status is 'orphan'.
 * **ro_reason** is ``nil`` if the instance is in writable mode.
-  When the field is ``true``, it reports an error reason.
+  When the field is not ``nil``, it contains a reason why the instance is read-only.
+  Possible error reasons: ``election``, ``synchro``, ``config``, and ``orphan``
+  (see :ref:`box.info.ro_reason <box_info_ro-reason>` for details).
 * **signature** is the sum of all ``lsn`` values from each :ref:`vector clock <replication-vector>`
   (**vclock**) for all instances in the replica set.
 * **sql().cache.size** is the number of bytes in the SQL prepared statement cache.
@@ -98,7 +100,7 @@ Below is a list of all ``box.info`` functions and members.
            - Show the current state of synchronous replication
 
         *  - :doc:`./box_info/ro_reason`
-           - List of all error reasons for the ``box.info.ro_reason`` field
+           - Show the current mode of an instance (writable or read-only)
 
 ..  toctree::
     :hidden:

doc/reference/reference_lua/box_info/ro_reason.rst

@@ -6,6 +6,13 @@ box.info.ro_reason
 
 ..  module:: box.info
 
+.. data:: ro_reason
+
+    Since :doc:`2.10.0 </release/2.10.0>`.
+    Show the current mode of an instance (writable or read-only).
+    Contains ``nil`` if the instance is in writable mode.
+    When the field is not ``nil``, it reports a reason why the instance is read-only.
+
     Possible error reasons:
 
     *   ``election`` -- the instance is not a leader.
@@ -20,3 +27,14 @@ box.info.ro_reason
 
     *   ``orphan`` -- the instance is in ``orphan`` state.
         For details, see :ref:`the orphan status page <internals-replication-orphan_status>`.
+
+    :rtype: string
+
+    **Example:**
+
+    ..  code-block:: tarantoolsession
+
+        tarantool> box.info.ro_reason
+        ---
+        - null
+        ...