diff --git a/ml-algorithms/src/main/java/org/opensearch/ml/engine/tools/SearchIndexTool.java b/ml-algorithms/src/main/java/org/opensearch/ml/engine/tools/SearchIndexTool.java
index 736cdc5a53..c617951b4a 100644
--- a/ml-algorithms/src/main/java/org/opensearch/ml/engine/tools/SearchIndexTool.java
+++ b/ml-algorithms/src/main/java/org/opensearch/ml/engine/tools/SearchIndexTool.java
@@ -62,6 +62,7 @@ public class SearchIndexTool implements Tool {
     public static final String INPUT_FIELD = "input";
     public static final String INDEX_FIELD = "index";
     public static final String QUERY_FIELD = "query";
+    public static final String SIZE_FIELD = "size";
     public static final String INPUT_SCHEMA_FIELD = "input_schema";
     public static final String STRICT_FIELD = "strict";
 
@@ -131,10 +132,13 @@ public boolean validate(Map<String, String> parameters) {
         return true;
     }
 
-    private SearchRequest getSearchRequest(String index, String query) throws IOException {
+    private SearchRequest getSearchRequest(String index, String query, Integer size) throws IOException {
         SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
         XContentParser queryParser = XContentType.JSON.xContent().createParser(xContentRegistry, LoggingDeprecationHandler.INSTANCE, query);
         searchSourceBuilder.parseXContent(queryParser);
+        if (size != null && size > 0) {
+            searchSourceBuilder.size(size);
+        }
         return new SearchRequest().source(searchSourceBuilder).indices(index);
     }
 
@@ -176,6 +180,7 @@ public <T> void run(Map<String, String> originalParameters, ActionListener<T> li
             String input = parameters.get(INPUT_FIELD);
             String index = null;
             String query = null;
+            Integer size = null;
             boolean returnFullResponse = Boolean.parseBoolean(parameters.getOrDefault(RETURN_RAW_RESPONSE, "false"));
             if (!StringUtils.isEmpty(input)) {
                 try {
@@ -188,6 +193,10 @@ public <T> void run(Map<String, String> originalParameters, ActionListener<T> li
                             Object queryObject = PLAIN_NUMBER_GSON.fromJson(queryElement, Object.class);
                             query = PLAIN_NUMBER_GSON.toJson(queryObject);
                         }
+
+                        if (jsonObject.has(SIZE_FIELD)) {
+                            size = jsonObject.get(SIZE_FIELD).getAsInt();
+                        }
                     }
                 } catch (JsonSyntaxException e) {
                     log.error("Invalid JSON input: {}", input, e);
@@ -202,6 +211,14 @@ public <T> void run(Map<String, String> originalParameters, ActionListener<T> li
                 query = parameters.get(QUERY_FIELD);
             }
 
+            if (StringUtils.isNotEmpty(parameters.get(SIZE_FIELD))) {
+                try {
+                    size = Math.min(size == null ? 100 : size, Integer.parseInt(parameters.get(SIZE_FIELD)));
+                } catch (NumberFormatException e) {
+                    log.warn("Invalid size parameter: {}", parameters.get(SIZE_FIELD));
+                }
+            }
+
             if (StringUtils.isEmpty(index) || StringUtils.isEmpty(query)) {
                 listener
                     .onFailure(
@@ -212,7 +229,7 @@ public <T> void run(Map<String, String> originalParameters, ActionListener<T> li
                 return;
             }
 
-            SearchRequest searchRequest = getSearchRequest(index, query);
+            SearchRequest searchRequest = getSearchRequest(index, query, size);
 
             ActionListener<SearchResponse> actionListener = ActionListener.<SearchResponse>wrap(r -> {
                 SearchHit[] hits = r.getHits().getHits();
diff --git a/ml-algorithms/src/test/java/org/opensearch/ml/engine/tools/SearchIndexToolTests.java b/ml-algorithms/src/test/java/org/opensearch/ml/engine/tools/SearchIndexToolTests.java
index 161c43a92f..97023d28fd 100644
--- a/ml-algorithms/src/test/java/org/opensearch/ml/engine/tools/SearchIndexToolTests.java
+++ b/ml-algorithms/src/test/java/org/opensearch/ml/engine/tools/SearchIndexToolTests.java
@@ -520,4 +520,44 @@ public void testRun_withRangeQuery_triggersPlainDoubleGson() {
 
         assertArrayEquals(new String[] { "test-index" }, cap.getValue().indices());
     }
+
+    @Test
+    public void testRunWithSizeInInput() {
+        String inputString = "{\"index\": \"test-index\", \"query\": {\"query\": {\"match_all\": {}}}, \"size\": 5}";
+        Map<String, String> parameters = Map.of("input", inputString);
+        mockedSearchIndexTool.run(parameters, null);
+        
+        ArgumentCaptor<SearchRequest> cap = ArgumentCaptor.forClass(SearchRequest.class);
+        verify(client, times(1)).search(cap.capture(), any());
+        assertEquals(5, cap.getValue().source().size());
+    }
+
+    @Test
+    public void testRunWithSizeAsParameter() {
+        Map<String, String> parameters = Map.of(
+            "index", "test-index", 
+            "query", "{\"query\": {\"match_all\": {}}}",
+            "size", "3"
+        );
+        mockedSearchIndexTool.run(parameters, null);
+        
+        ArgumentCaptor<SearchRequest> cap = ArgumentCaptor.forClass(SearchRequest.class);
+        verify(client, times(1)).search(cap.capture(), any());
+        assertEquals(3, cap.getValue().source().size());
+    }
+
+    @Test
+    public void testRunWithInvalidSizeParameter() {
+        Map<String, String> parameters = Map.of(
+            "index", "test-index", 
+            "query", "{\"query\": {\"match_all\": {}}}",
+            "size", "invalid"
+        );
+        mockedSearchIndexTool.run(parameters, null);
+        
+        ArgumentCaptor<SearchRequest> cap = ArgumentCaptor.forClass(SearchRequest.class);
+        verify(client, times(1)).search(cap.capture(), any());
+        // Size should not be set when invalid
+        assertEquals(-1, cap.getValue().source().size());
+    }
 }