diff --git a/api/services/summary_index_service.py b/api/services/summary_index_service.py
index 12053377e2..8760d60de0 100644
--- a/api/services/summary_index_service.py
+++ b/api/services/summary_index_service.py
@@ -4,7 +4,7 @@ import logging
 import time
 import uuid
 from datetime import UTC, datetime
-from typing import Any
+from typing import TypedDict, cast
 
 from graphon.model_runtime.entities.llm_entities import LLMUsage
 from graphon.model_runtime.entities.model_entities import ModelType
@@ -25,6 +25,22 @@ from models.enums import SummaryStatus
 logger = logging.getLogger(__name__)
 
 
+class SummaryEntryDict(TypedDict):
+    segment_id: str
+    segment_position: int
+    status: str
+    summary_preview: str | None
+    error: str | None
+    created_at: int | None
+    updated_at: int | None
+
+
+class DocumentSummaryStatusDetailDict(TypedDict):
+    total_segments: int
+    summary_status: dict[str, int]
+    summaries: list[SummaryEntryDict]
+
+
 class SummaryIndexService:
     """Service for generating and managing summary indexes."""
 
@@ -1352,7 +1368,7 @@ class SummaryIndexService:
     def get_document_summary_status_detail(
         document_id: str,
         dataset_id: str,
-    ) -> dict[str, Any]:
+    ) -> DocumentSummaryStatusDetailDict:
         """
         Get detailed summary status for a document.
 
@@ -1403,7 +1419,7 @@ class SummaryIndexService:
             SummaryStatus.NOT_STARTED: 0,
         }
 
-        summary_list = []
+        summary_list: list[SummaryEntryDict] = []
         for segment in segments:
             summary = summary_map.get(segment.id)
             if summary:
@@ -1438,8 +1454,8 @@ class SummaryIndexService:
                     }
                 )
 
-        return {
-            "total_segments": total_segments,
-            "summary_status": status_counts,
-            "summaries": summary_list,
-        }
+        return DocumentSummaryStatusDetailDict(
+            total_segments=total_segments,
+            summary_status=cast(dict[str, int], status_counts),
+            summaries=summary_list,
+        )