diff --git a/src/strands_tools/retrieve.py b/src/strands_tools/retrieve.py
index 3d903aca..de1e40a2 100644
--- a/src/strands_tools/retrieve.py
+++ b/src/strands_tools/retrieve.py
@@ -166,6 +166,20 @@
                     ),
                     "default": False,
                 },
+                "retrieveFilter": {
+                    "type": "object",
+                    "description": (
+                        "Optional filter to apply to retrieval results based on metadata attributes in the "
+                        "knowledge base. This is a UNION type - only one operator can be specified at the top level. "
+                        "Available operators: "
+                        "equals (exact match), notEquals, greaterThan, greaterThanOrEquals, lessThan, "
+                        "lessThanOrEquals, in (value in list), notIn, listContains (list contains value), "
+                        "stringContains (substring match), startsWith (OpenSearch Serverless only), "
+                        "andAll (all conditions must match, min 2 items), orAll (at least one condition must match, "
+                        "min 2 items). Example: {\"andAll\": [{\"equals\": {\"key\": \"category\", "
+                        "\"value\": \"security\"}}, {\"greaterThan\": {\"key\": \"year\", \"value\": \"2022\"}}]}"
+                    ),
+                },
             },
             "required": ["text"],
         }