diff --git a/changedetectionio/api/Tags.py b/changedetectionio/api/Tags.py
index f09a5ef8a..33791e346 100644
--- a/changedetectionio/api/Tags.py
+++ b/changedetectionio/api/Tags.py
@@ -67,7 +67,25 @@ class Tag(Resource):
             tag.commit()
             return "OK", 200
 
-        return tag
+        # Filter out Watch-specific runtime fields that don't apply to Tags (yet)
+        # TODO: Future enhancement - aggregate these values from all Watches that have this tag:
+        #   - check_count: sum of all watches' check_count
+        #   - last_checked: most recent last_checked from all watches
+        #   - last_changed: most recent last_changed from all watches
+        #   - consecutive_filter_failures: count of watches with failures
+        #   - etc.
+        # These come from watch_base inheritance but currently have no meaningful value for Tags
+        watch_only_fields = {
+            'browser_steps_last_error_step', 'check_count', 'consecutive_filter_failures',
+            'content-type', 'fetch_time', 'last_changed', 'last_checked', 'last_error',
+            'last_notification_error', 'last_viewed', 'notification_alert_count',
+            'page_title', 'previous_md5', 'previous_md5_before_filters', 'remote_server_reply'
+        }
+
+        # Create clean tag dict without Watch-specific fields
+        clean_tag = {k: v for k, v in tag.items() if k not in watch_only_fields}
+
+        return clean_tag
 
     @auth.check_token
     @validate_openapi_request('deleteTag')
diff --git a/changedetectionio/tests/test_api_tags.py b/changedetectionio/tests/test_api_tags.py
index 8622fcf80..bf2823efd 100644
--- a/changedetectionio/tests/test_api_tags.py
+++ b/changedetectionio/tests/test_api_tags.py
@@ -207,7 +207,8 @@ def test_roundtrip_API(client, live_server, measure_memory_usage, datastore_path
 
     tag = res.json
 
-    tag['last_changed'] = 454444444444
+    # Only test with date_created (readOnly field that should be filtered out)
+    # last_changed is Watch-specific and doesn't apply to Tags
     tag['date_created'] = 454444444444
 
     # HTTP PUT ( UPDATE an existing watch )
@@ -221,14 +222,11 @@ def test_roundtrip_API(client, live_server, measure_memory_usage, datastore_path
         print(f"Error: {res.data}")
     assert res.status_code == 200, "HTTP PUT update was sent OK"
 
+    # Verify readOnly fields like date_created cannot be overridden
     res = client.get(
-        url_for("watch", uuid=uuid),
+        url_for("tag", uuid=uuid),
         headers={'x-api-key': api_key}
     )
-    last_changed = res.json.get('last_changed')
-    assert last_changed != 454444444444
-    assert last_changed != "454444444444"
-
     date_created = res.json.get('date_created')
-    assert date_created != 454444444444
-    assert date_created != "454444444444"
+    assert date_created != 454444444444, "ReadOnly date_created should not be updateable"
+    assert date_created != "454444444444", "ReadOnly date_created should not be updateable"
diff --git a/docs/api-spec.yaml b/docs/api-spec.yaml
index 25334be4f..daac3b7e7 100644
--- a/docs/api-spec.yaml
+++ b/docs/api-spec.yaml
@@ -566,8 +566,28 @@ components:
         - type: object
           properties:
             overrides_watch:
-              type: boolean
-              description: If true, this tag's settings override watch settings for all watches in this tag/group
+              type: [boolean, 'null']
+              description: |
+                Whether this tag's settings override watch settings for all watches in this tag/group.
+                - true: Tag settings override watch settings
+                - false: Tag settings do not override (watches use their own settings)
+                - null: Not decided yet / inherit default behavior
+            # Future: Aggregated statistics from all watches with this tag
+            # check_count:
+            #   type: integer
+            #   description: Sum of check_count from all watches with this tag
+            #   readOnly: true
+            #   x-computed: true
+            # last_checked:
+            #   type: integer
+            #   description: Most recent last_checked timestamp from all watches with this tag
+            #   readOnly: true
+            #   x-computed: true
+            # last_changed:
+            #   type: integer
+            #   description: Most recent last_changed timestamp from all watches with this tag
+            #   readOnly: true
+            #   x-computed: true
 
     CreateTag:
       allOf: