diff --git a/src/types/content.ts b/src/types/content.ts
index 3a3073f0..2a858782 100644
--- a/src/types/content.ts
+++ b/src/types/content.ts
@@ -459,6 +459,8 @@ export declare interface UsageMetadata {
   candidatesTokenCount?: number;
   /** Optional. Total number of tokens. */
   totalTokenCount?: number;
+  /** Optional. Number of tokens in the cached content. */
+  cachedContentTokenCount?: number;
 }
 
 /**