diff --git a/docs/index.md b/docs/index.md
index 055756e4c..b1bf5478d 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -514,7 +514,8 @@ In the index mapping, the `_meta` and `properties`field stores meta and schema i
 - `spark.datasource.flint.retry.max_retries`: max retries on failed HTTP request. default value is 3. Use 0 to disable retry.
 - `spark.datasource.flint.retry.http_status_codes`: retryable HTTP response status code list. default value is "429,502" (429 Too Many Request and 502 Bad Gateway).
 - `spark.datasource.flint.retry.exception_class_names`: retryable exception class name list. by default no retry on any exception thrown.
-- `spark.flint.optimizer.enabled`: default is true.
+- `spark.flint.optimizer.enabled`: default is true. enable the Flint optimizer for improving query performance.
+- `spark.flint.optimizer.covering.enabled`: default is true. enable the Flint covering index optimizer for improving query performance.
 - `spark.flint.index.hybridscan.enabled`: default is false.
 - `spark.flint.index.checkpoint.mandatory`: default is true.
 - `spark.datasource.flint.socket_timeout_millis`: default value is 60000.
diff --git a/flint-spark-integration/src/main/scala/org/opensearch/flint/spark/covering/ApplyFlintSparkCoveringIndex.scala b/flint-spark-integration/src/main/scala/org/opensearch/flint/spark/covering/ApplyFlintSparkCoveringIndex.scala
index c8cb62b2c..f917f9c98 100644
--- a/flint-spark-integration/src/main/scala/org/opensearch/flint/spark/covering/ApplyFlintSparkCoveringIndex.scala
+++ b/flint-spark-integration/src/main/scala/org/opensearch/flint/spark/covering/ApplyFlintSparkCoveringIndex.scala
@@ -27,19 +27,9 @@ import org.apache.spark.sql.util.CaseInsensitiveStringMap
  */
 class ApplyFlintSparkCoveringIndex(flint: FlintSpark) extends Rule[LogicalPlan] {
 
-  /**
-   * Prerequisite:
-   * ```
-   *   1) Not an insert statement
-   *   2) Relation is supported, ex. Iceberg, Delta, File. (is this check required?)
-   *   3) Any covering index on the table:
-   *     3.1) doesn't have filtering condition
-   *     3.2) cover all columns present in the query
-   * ```
-   */
   override def apply(plan: LogicalPlan): LogicalPlan = plan transform {
     case relation @ LogicalRelation(_, _, Some(table), false)
-        if !plan.isInstanceOf[V2WriteCommand] =>
+        if !plan.isInstanceOf[V2WriteCommand] => // Not an insert statement
       val tableName = table.qualifiedName
       val requiredCols = collectAllColumnsInQueryPlan(plan)
 
@@ -74,7 +64,7 @@ class ApplyFlintSparkCoveringIndex(flint: FlintSpark) extends Rule[LogicalPlan]
       index: FlintSparkCoveringIndex,
       requiredCols: Set[String]): Boolean = {
     index.latestLogEntry.exists(_.state != DELETED) &&
-    index.filterCondition.isEmpty &&
+    index.filterCondition.isEmpty && // TODO: support partial covering index later
     requiredCols.subsetOf(index.indexedColumns.keySet)
   }
 
@@ -87,7 +77,9 @@ class ApplyFlintSparkCoveringIndex(flint: FlintSpark) extends Rule[LogicalPlan]
     val inferredSchema = ds.inferSchema(options)
     val flintTable = ds.getTable(inferredSchema, Array.empty, options)
 
-    // Keep original output attributes in index only
+    // Keep original output attributes only if available in covering index.
+    // We have to reuse original attribute object because it's already analyzed
+    // with exprId referenced by the other parts of the query plan.
     val outputAttributes =
       index.indexedColumns.keys
         .map(colName => relation.output.find(_.name == colName).get)
diff --git a/flint-spark-integration/src/test/scala/org/opensearch/flint/spark/covering/ApplyFlintSparkCoveringIndexSuite.scala b/flint-spark-integration/src/test/scala/org/opensearch/flint/spark/covering/ApplyFlintSparkCoveringIndexSuite.scala
index 6a64be925..bd0d8225b 100644
--- a/flint-spark-integration/src/test/scala/org/opensearch/flint/spark/covering/ApplyFlintSparkCoveringIndexSuite.scala
+++ b/flint-spark-integration/src/test/scala/org/opensearch/flint/spark/covering/ApplyFlintSparkCoveringIndexSuite.scala
@@ -71,7 +71,7 @@ class ApplyFlintSparkCoveringIndexSuite extends FlintSuite with Matchers {
       .assertIndexNotUsed()
   }
 
-  // Covering index doesn't column age
+  // Covering index doesn't cover column age
   Seq(
     s"SELECT * FROM $testTable",
     s"SELECT name, age FROM $testTable",