diff --git a/swh/storage/in_memory.py b/swh/storage/in_memory.py
--- a/swh/storage/in_memory.py
+++ b/swh/storage/in_memory.py
@@ -921,11 +921,14 @@
             'directory',
             'origin',
             'origin_visit',
+            'origin_metadata',
             'person',
             'release',
             'revision',
             'skipped_content',
-            'snapshot'
+            'snapshot',
+            'tool',
+            'metadata_provider'
             )
         stats = {key: 0 for key in keys}
         stats.update(collections.Counter(
@@ -951,7 +954,9 @@
                 'metadata': metadata,
                 'provider_id': provider,
                 }
+
         self._origin_metadata[origin_url].append(origin_metadata)
+        self._objects[origin_url].append(("origin_metadata", origin_url))
         return None
 
     def origin_metadata_get_by(self, origin_url, provider_type=None):
@@ -977,6 +982,7 @@
             if key not in self._tools:
                 self._tools[key] = record
             inserted.append(copy.deepcopy(self._tools[key]))
+            self._objects[key].append(("tool", key))
 
         return inserted
 
@@ -993,7 +999,9 @@
                 }
         key = self._metadata_provider_key(provider)
         provider['id'] = key
+
         self._metadata_providers[key] = provider
+        self._objects[key].append(("metadata_provider", provider['id']))
         return key
 
     def metadata_provider_get(self, provider_id):
diff --git a/swh/storage/tests/test_storage.py b/swh/storage/tests/test_storage.py
--- a/swh/storage/tests/test_storage.py
+++ b/swh/storage/tests/test_storage.py
@@ -3019,6 +3019,9 @@
         assert new_id == new_id2
         assert actual_tool == actual_tool2
 
+        swh_storage.refresh_stat_counters()
+        assert swh_storage.stat_counters()['tool'] == 2
+
     def test_tool_add_multiple(self, swh_storage):
         tool = {
             'name': 'some-unknown-tool',
@@ -3158,6 +3161,9 @@
         # then
         assert n_actual_om == n_om + 2
 
+        swh_storage.refresh_stat_counters()
+        assert swh_storage.stat_counters()['origin_metadata'] == 2
+
     def test_origin_metadata_get(self, swh_storage):
         # given
         origin_url = data.origin['url']
@@ -3249,6 +3255,9 @@
              'provider_url': 'http://www.swmath.org/'})
         assert provider == swh_storage.metadata_provider_get(provider_id)
 
+        swh_storage.refresh_stat_counters()
+        assert swh_storage.stat_counters()['metadata_provider'] == 1
+
     def test_origin_metadata_get_by_provider_type(self, swh_storage):
         # given
         origin_url = data.origin['url']