diff --git a/src/types.ts b/src/types.ts
index 7f168d8..0b15454 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -27,4 +27,5 @@ export interface McpInstallation {
   mcpTokens: OAuthTokens;
   clientId: string;
   issuedAt: number;
+  userId: string; // Unique identifier for the user (not client)
 }
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