diff --git a/x-pack/packages/kbn-elastic-assistant/impl/knowledge_base/knowledge_base_settings_management/index_entry_editor.tsx b/x-pack/packages/kbn-elastic-assistant/impl/knowledge_base/knowledge_base_settings_management/index_entry_editor.tsx
index 00baca022eed2..b55fb4b1b8270 100644
--- a/x-pack/packages/kbn-elastic-assistant/impl/knowledge_base/knowledge_base_settings_management/index_entry_editor.tsx
+++ b/x-pack/packages/kbn-elastic-assistant/impl/knowledge_base/knowledge_base_settings_management/index_entry_editor.tsx
@@ -273,6 +273,7 @@ export const IndexEntryEditor: React.FC<Props> = React.memo(
           fullWidth
           isInvalid={isMissingIndex}
           error={isMissingIndex && <>{i18n.MISSING_INDEX_ERROR}</>}
+          helpText={i18n.ENTRY_INDEX_NAME_INPUT_DESCRIPTION}
         >
           <EuiComboBox
             data-test-subj="index-combobox"
diff --git a/x-pack/packages/kbn-elastic-assistant/impl/knowledge_base/knowledge_base_settings_management/translations.ts b/x-pack/packages/kbn-elastic-assistant/impl/knowledge_base/knowledge_base_settings_management/translations.ts
index 98af0eabea6b5..24784586edcdf 100644
--- a/x-pack/packages/kbn-elastic-assistant/impl/knowledge_base/knowledge_base_settings_management/translations.ts
+++ b/x-pack/packages/kbn-elastic-assistant/impl/knowledge_base/knowledge_base_settings_management/translations.ts
@@ -234,6 +234,14 @@ export const ENTRY_INDEX_NAME_INPUT_LABEL = i18n.translate(
   }
 );
 
+export const ENTRY_INDEX_NAME_INPUT_DESCRIPTION = i18n.translate(
+  'xpack.elasticAssistant.assistant.settings.knowledgeBaseSettingsManagement.entryIndexNameInputDescription',
+  {
+    defaultMessage:
+      'Indices will only be available to select from this drop down list if they contain a semantic_text field. Please refer to the documentation for more information on configuring an index for use as a custom knowledge source.',
+  }
+);
+
 export const ENTRY_FIELD_INPUT_LABEL = i18n.translate(
   'xpack.elasticAssistant.assistant.settings.knowledgeBaseSettingsManagement.entryFieldInputLabel',
   {