diff --git a/output/elasticsearch.md b/output/elasticsearch.md
index fb10a4c4..f9866f60 100644
--- a/output/elasticsearch.md
+++ b/output/elasticsearch.md
@@ -114,6 +114,8 @@ For more information about buffer options checkout the [Buffer Section Configura
 
 If `true`, Fluentd uses the conventional index name format `logstash-%Y.%m.%d` \(default: `false`\). This option supersedes the `index_name` option.
 
+When `true`, the plugin also adds a `@timestamp` field to records that do not already have one, which Kibana can use as the time field. With the default `false`, this field is only added if [`include_timestamp`](https://github.com/uken/fluent-plugin-elasticsearch#include_timestamp) is `true`.
+
 #### `@log_level` option
 
 The `@log_level` option allows the user to set different levels of logging for each plugin.
diff --git a/output/opensearch.md b/output/opensearch.md
index 92263834..94fec549 100644
--- a/output/opensearch.md
+++ b/output/opensearch.md
@@ -116,6 +116,8 @@ For more information about buffer options checkout the [Buffer Section Configura
 
 If `true`, Fluentd uses the conventional index name format `logstash-%Y.%m.%d` \(default: `false`\). This option supersedes the `index_name` option.
 
+When `true`, the plugin also adds a `@timestamp` field to records that do not already have one, which OpenSearch Dashboards can use as the time field. With the default `false`, this field is only added if [`include_timestamp`](https://github.com/fluent/fluent-plugin-opensearch#include_timestamp) is `true`.
+
 #### `@log_level` option
 
 The `@log_level` option allows the user to set different levels of logging for each plugin.