diff --git a/src/interfaces/http-error.ts b/src/interfaces/http-error.ts
index 8abe48b..787b79c 100644
--- a/src/interfaces/http-error.ts
+++ b/src/interfaces/http-error.ts
@@ -1,14 +1,16 @@
 import HttpStatus from "./http-status";
 
+type DevMessage = "missing_or_invalid_parameter" | "data_exists" | "unknown_url" | "data_not_found";
+
 class HttpError extends Error {
   /**
    * HTTP Status Code
    */
   status: HttpStatus;
   message: string;
-  devMessage?: string;
+  devMessage?: DevMessage;
 
-  constructor(status: HttpStatus, message: string, devMessage?: string) {
+  constructor(status: HttpStatus, message: string, devMessage?: DevMessage) {
     super(message);
 
     this.name = "HttpError";