diff --git a/src/server/common/index.ts b/src/server/common/index.ts
new file mode 100644
index 00000000..e4c80b6a
--- /dev/null
+++ b/src/server/common/index.ts
@@ -0,0 +1,13 @@
+export enum Status {
+  // Accepted status
+  OK = 200,
+
+  // Client-error status
+  BAD_REQUEST = 400,
+  UNAUTHORIZED = 401,
+  NOT_FOUND = 404,
+
+  // Server-error status
+  INTERNAL_SERVER_ERROR = 500,
+  NOT_IMPLEMENTED = 501,
+}
diff --git a/src/types/fetch.d.ts b/src/types/fetch.d.ts
new file mode 100644
index 00000000..5cb2d7e7
--- /dev/null
+++ b/src/types/fetch.d.ts
@@ -0,0 +1,11 @@
+/**
+ * Extends fetch input parameters.
+ */
+interface ExtendedRequestInit extends RequestInit {
+  method?: "GET" | "POST" | "PUT" | "PATCH" | "DELETE";
+}
+
+declare function fetch(
+  input: URL | RequestInfo,
+  init?: ExtendedRequestInit
+): Promise<Response>;