diff --git a/api-ref/source/diagnostics.inc b/api-ref/source/diagnostics.inc
index fa37489be24..b5e63b05861 100644
--- a/api-ref/source/diagnostics.inc
+++ b/api-ref/source/diagnostics.inc
@@ -53,7 +53,7 @@ will be reported as ``None`` in the response.
   - disk_details: disk_details_diagnostics
   - nic_details: nic_details_diagnostics
 
-**Example Server diagnostics**
+**Example Server diagnostics (2.48)**
 
 .. literalinclude:: ../../doc/api_samples/os-server-diagnostics/v2.48/server-diagnostics-get-resp.json
    :language: javascript
@@ -62,7 +62,7 @@ will be reported as ``None`` in the response.
    Before **microversion 2.48** the response format for diagnostics was not
    well defined. Each hypervisor had its own format.
 
-**Example Old Server diagnostics**
+**Example Server diagnostics (2.1)**
 
 Below is an example of diagnostics for a libvirt based instance. The unit of the return
 value is hypervisor specific, but in this case the unit of vnet1_rx* and
diff --git a/nova/api/openstack/compute/rest_api_version_history.rst b/nova/api/openstack/compute/rest_api_version_history.rst
index 29ceffda16a..349afdfb53c 100644
--- a/nova/api/openstack/compute/rest_api_version_history.rst
+++ b/nova/api/openstack/compute/rest_api_version_history.rst
@@ -562,5 +562,5 @@ user documentation.
   Before version 2.48, VM diagnostics response was just a 'blob' of data
   returned by each hypervisor. From this version VM diagnostics response is
   standardized. It has a set of fields which each hypervisor will try to fill.
-  If a hypervisor driver unable to provide a specific field then this field
+  If a hypervisor driver is unable to provide a specific field then this field
   will be reported as 'None'.
diff --git a/nova/api/openstack/compute/server_diagnostics.py b/nova/api/openstack/compute/server_diagnostics.py
index 9279e56ce49..eca71a56399 100644
--- a/nova/api/openstack/compute/server_diagnostics.py
+++ b/nova/api/openstack/compute/server_diagnostics.py
@@ -58,10 +58,10 @@ def index(self, req, server_id):
             # Diagnostics object. Old compute returns a dictionary. So we
             # can't perform a request correctly if compute is too old.
             msg = _('Compute node is too old. You must complete the '
-                    'upgrade process to be able to get a standardized '
+                    'upgrade process to be able to get standardized '
                     'diagnostics data which is available since v2.48. However '
-                    'you still able to get a diagnostics data in old format '
-                    'which is available till v2.47.')
+                    'you are still able to get diagnostics data in '
+                    'non-standardized format which is available until v2.47.')
             raise webob.exc.HTTPBadRequest(explanation=msg)
         except NotImplementedError:
             common.raise_feature_not_supported()
diff --git a/nova/exception.py b/nova/exception.py
index 89c470b89d3..6bde3c0bb14 100644
--- a/nova/exception.py
+++ b/nova/exception.py
@@ -2021,7 +2021,7 @@ class AttachInterfaceNotSupported(Invalid):
 
 
 class InstanceDiagnosticsNotSupported(Invalid):
-    msg_fmt = _("Instance diagnostics is not supported by compute node.")
+    msg_fmt = _("Instance diagnostics are not supported by compute node.")
 
 
 class InvalidReservedMemoryPagesOption(Invalid):
diff --git a/releasenotes/notes/bp-restore-vm-diagnostics-544b56bbb0167071.yaml b/releasenotes/notes/bp-restore-vm-diagnostics-544b56bbb0167071.yaml
index bdf2f3e3645..d8650373879 100644
--- a/releasenotes/notes/bp-restore-vm-diagnostics-544b56bbb0167071.yaml
+++ b/releasenotes/notes/bp-restore-vm-diagnostics-544b56bbb0167071.yaml
@@ -2,5 +2,5 @@
 features:
   - Added microversion v2.48 which standardize VM diagnostics response.
     It has a set of fields which each hypervisor will try to fill.
-    If a hypervisor driver unable to provide a specific field then this field
-    will be reported as 'None'.
+    If a hypervisor driver is unable to provide a specific field then this
+    field will be reported as 'None'.