diff --git a/lexicons/io/atcr/manifest.json b/lexicons/io/atcr/manifest.json
index b080c21..57ca0f4 100644
--- a/lexicons/io/atcr/manifest.json
+++ b/lexicons/io/atcr/manifest.json
@@ -65,8 +65,8 @@
             "description": "Referenced manifests (for manifest lists/indexes)"
           },
           "annotations": {
-            "type": "object",
-            "description": "Optional metadata annotations"
+            "type": "unknown",
+            "description": "Optional OCI annotation metadata. Map of string keys to string values (e.g., org.opencontainers.image.title → 'My App')."
           },
           "subject": {
             "type": "ref",
@@ -111,8 +111,8 @@
           "description": "Optional direct URLs to blob (for BYOS)"
         },
         "annotations": {
-          "type": "object",
-          "description": "Optional metadata"
+          "type": "unknown",
+          "description": "Optional OCI annotation metadata. Map of string keys to string values."
         }
       }
     },
@@ -139,8 +139,8 @@
           "description": "Platform information for this manifest"
         },
         "annotations": {
-          "type": "object",
-          "description": "Optional metadata"
+          "type": "unknown",
+          "description": "Optional OCI annotation metadata. Map of string keys to string values."
         }
       }
     },