diff --git a/package.json b/package.json
index 669a438..fb19d56 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "type": "commonjs",
   "name": "@riq0h/mtt",
-  "version": "0.0.9",
+  "version": "0.0.10",
   "description": "mtt - multitool for file operation",
   "main": "dist/lib.js",
   "types": "dist/lib.d.ts",
diff --git a/src/commands/compress.ts b/src/commands/compress.ts
index c63c38b..e295e78 100644
--- a/src/commands/compress.ts
+++ b/src/commands/compress.ts
@@ -12,18 +12,22 @@ export async function compressFiles(targets?: string[]): Promise<void> {
     const currentDir = process.cwd();
     let isCompressed = false;
 
-    const itemsToCompress =
+    const itemsToCompress: string[] =
       !targets || targets.length === 0
         ? fs
             .readdirSync(currentDir)
-            .filter((item) => !item.startsWith(".") && !item.endsWith(".zip"))
+            .filter(
+              (item: string) => !item.startsWith(".") && !item.endsWith(".zip"),
+            )
         : targets;
 
-    const operations: CompressOperation[] = itemsToCompress.map((item) => ({
-      itemPath: item,
-      zipPath: `${item}.zip`,
-      isFile: fs.existsSync(item) ? fs.statSync(item).isFile() : false,
-    }));
+    const operations: CompressOperation[] = itemsToCompress.map(
+      (item: string) => ({
+        itemPath: item,
+        zipPath: `${item}.zip`,
+        isFile: fs.existsSync(item) ? fs.statSync(item).isFile() : false,
+      }),
+    );
 
     for (const op of operations) {
       if (fs.existsSync(op.zipPath)) {
diff --git a/src/commands/rename.ts b/src/commands/rename.ts
index 9897bdf..f3d9bd9 100644
--- a/src/commands/rename.ts
+++ b/src/commands/rename.ts
@@ -11,12 +11,12 @@ export interface RenameOperation {
 
 export async function renameFiles(): Promise<void> {
   try {
-    const files = fs
+    const files: string[] = fs
       .readdirSync(process.cwd())
-      .filter((file) => !file.startsWith("."));
-    const fileContent = files.join("\n");
-    const editedContent = await openEditor(fileContent);
-    const newNames = editedContent.trim().split("\n");
+      .filter((file: string) => !file.startsWith("."));
+    const fileContent: string = files.join("\n");
+    const editedContent: string = await openEditor(fileContent);
+    const newNames: string[] = editedContent.trim().split("\n");
 
     if (newNames.length !== files.length) {
       throw new Error(
@@ -24,18 +24,18 @@ export async function renameFiles(): Promise<void> {
       );
     }
 
-    const uniqueNames = new Set(newNames);
+    const uniqueNames: Set<string> = new Set(newNames);
     if (uniqueNames.size !== newNames.length) {
       throw new Error("file names are duplicated. renaming was not performed.");
     }
 
-    if (newNames.some((name) => /[\s　]/.test(name))) {
+    if (newNames.some((name: string) => /[\s　]/.test(name))) {
       throw new Error(
         "file names cannot contain whitespace characters. renaming was not performed.",
       );
     }
 
-    newNames.forEach((name) => {
+    newNames.forEach((name: string) => {
       if (name.includes("/") || name.includes("\\")) {
         throw new Error(
           "file names cannot contain paths. renaming was not performed.",
@@ -43,14 +43,16 @@ export async function renameFiles(): Promise<void> {
       }
     });
 
-    const operations = files.map((oldName, index) => ({
-      oldName,
-      newName: newNames[index],
-      path: path.join(process.cwd(), oldName),
-      newPath: path.join(process.cwd(), newNames[index]),
-    }));
+    const operations: RenameOperation[] = files.map(
+      (oldName: string, index: number) => ({
+        oldName,
+        newName: newNames[index],
+        path: path.join(process.cwd(), oldName),
+        newPath: path.join(process.cwd(), newNames[index]),
+      }),
+    );
 
-    if (!operations.some((op) => op.oldName !== op.newName)) {
+    if (!operations.some((op: RenameOperation) => op.oldName !== op.newName)) {
       console.log("no changes were made. renaming was not performed.");
       return;
     }
diff --git a/src/commands/resize.ts b/src/commands/resize.ts
index 177105c..83c561e 100644
--- a/src/commands/resize.ts
+++ b/src/commands/resize.ts
@@ -21,7 +21,7 @@ export async function resizeImages(
     }
 
     const imageExtensions = [".jpg", ".jpeg", ".png", ".gif", ".webp"];
-    const validFiles = files.filter((file) =>
+    const validFiles = files.filter((file: string) =>
       imageExtensions.includes(path.extname(file).toLowerCase()),
     );
 
diff --git a/src/index.ts b/src/index.ts
index 3797f44..e49192e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -3,6 +3,13 @@ import { Command } from "commander";
 import { version, description } from "../package.json";
 import { renameFiles, compressFiles, resizeImages } from "./lib";
 
+interface Options {
+  rename?: boolean;
+  compress?: boolean | string[];
+  image?: string[];
+  percentage?: number;
+}
+
 const program = new Command();
 
 program.version(version).description(description);
@@ -18,7 +25,7 @@ program
     "resize image files. File name and -p option are required",
   )
   .option("-p, --percentage <value>", "specify the resize percentage")
-  .action((options) => {
+  .action((options: Options) => {
     try {
       if (options.rename) {
         renameFiles();
@@ -30,7 +37,7 @@ program
             "resize percentage must be specified with the -p option for image resizing.",
           );
         }
-        resizeImages(options.image, Number(options.percentage));
+        resizeImages(options.image, options.percentage);
       } else {
         program.help();
       }