diff --git a/app/src/api/admin.ts b/app/src/api/admin.ts
index f7de7b7..672145a 100644
--- a/app/src/api/admin.ts
+++ b/app/src/api/admin.ts
@@ -19,14 +19,8 @@ const ADMIN_BASE_URL = `${API_BASE_URL}/admin`;
  * */
 export const getUsers = async (): Promise<User[]> => {
   const response = await apiCall(`${ADMIN_BASE_URL}/users`);
-
-  if (!response.ok) {
-    const data = await response.json();
-    const errorData = data as { message: string };
-    throw new Error(errorData.message || 'Failed to fetch users');
-  }
-
   const data = await response.json();
+
   if (!Array.isArray(data)) {
     throw new Error('Invalid users response received from API');
   }
@@ -52,12 +46,6 @@ export const createUser = async (
     body: JSON.stringify(userData),
   });
 
-  if (!response.ok) {
-    const data = await response.json();
-    const errorData = data as { message: string };
-    throw new Error(errorData.message || 'Failed to create user');
-  }
-
   const data = await response.json();
   if (!isUser(data)) {
     throw new Error('Invalid user object received from API');
@@ -97,11 +85,6 @@ export const updateUser = async (
     body: JSON.stringify(userData),
   });
 
-  if (!response.ok) {
-    const data = await response.json();
-    const errorData = data as { message: string };
-    throw new Error(errorData.message || 'Failed to update user');
-  }
   const data = await response.json();
   if (!isUser(data)) {
     throw new Error('Invalid user object received from API');
@@ -118,11 +101,6 @@ export const updateUser = async (
  * */
 export const getWorkspaces = async (): Promise<Workspace[]> => {
   const response = await apiCall(`${ADMIN_BASE_URL}/workspaces`);
-  if (!response.ok) {
-    const data = await response.json();
-    const errorData = data as { message: string };
-    throw new Error(errorData.message || 'Failed to fetch workspaces');
-  }
   const data = await response.json();
   if (!Array.isArray(data)) {
     throw new Error('Invalid workspaces response received from API');
@@ -144,11 +122,6 @@ export const getWorkspaces = async (): Promise<Workspace[]> => {
  * */
 export const getSystemStats = async (): Promise<SystemStats> => {
   const response = await apiCall(`${ADMIN_BASE_URL}/stats`);
-  if (!response.ok) {
-    const data = await response.json();
-    const errorData = data as { message: string };
-    throw new Error(errorData.message || 'Failed to fetch system stats');
-  }
   const data = await response.json();
   if (!isSystemStats(data)) {
     throw new Error('Invalid system stats response received from API');
diff --git a/app/src/api/auth.ts b/app/src/api/auth.ts
index 6eb0a05..e76aaf3 100644
--- a/app/src/api/auth.ts
+++ b/app/src/api/auth.ts
@@ -4,13 +4,17 @@ import {
   LoginRequest,
   LoginResponse,
   isLoginResponse,
-  ErrorResponse,
   isUser,
 } from '../types/authApi';
 import { apiCall } from './api';
 
 /**
  * Logs in a user with email and password
+ * @param {string} email - The user's email
+ * @param {string} password - The user's password
+ * @returns {Promise<LoginResponse>} A promise that resolves to the login response
+ * @throws {Error} If the API call fails or returns an invalid response
+ * @throws {Error} If the login fails
  */
 export const login = async (
   email: string,
@@ -22,12 +26,6 @@ export const login = async (
     body: JSON.stringify(loginData),
   });
 
-  if (!response.ok) {
-    const data = await response.json();
-    const errorData = data as ErrorResponse;
-    throw new Error(errorData.message || 'Login failed');
-  }
-
   const data = await response.json();
   if (!isLoginResponse(data)) {
     throw new Error('Invalid login response received from API');
@@ -38,16 +36,17 @@ export const login = async (
 
 /**
  * Logs out the current user
+ * @returns {Promise<void>} A promise that resolves when the logout is successful
+ * @throws {Error} If the API call fails or returns an invalid response
+ * @throws {Error} If the logout fails
  */
 export const logout = async (): Promise<void> => {
   const response = await apiCall(`${API_BASE_URL}/auth/logout`, {
     method: 'POST',
   });
 
-  if (!response.ok) {
-    const data = await response.json();
-    const errorData = data as ErrorResponse;
-    throw new Error(errorData.message || 'Logout failed');
+  if (response.status !== 204) {
+    throw new Error('Failed to log out');
   }
 };
 
@@ -57,16 +56,10 @@ export const logout = async (): Promise<void> => {
  */
 export const refreshToken = async (): Promise<boolean> => {
   try {
-    const response = await apiCall(`${API_BASE_URL}/auth/refresh`, {
+    await apiCall(`${API_BASE_URL}/auth/refresh`, {
       method: 'POST',
     });
 
-    if (!response.ok) {
-      const data = await response.json();
-      const errorData = data as ErrorResponse;
-      throw new Error(errorData.message || 'Token refresh failed');
-    }
-
     return true;
   } catch (error) {
     return false;
@@ -75,16 +68,14 @@ export const refreshToken = async (): Promise<boolean> => {
 
 /**
  * Gets the currently authenticated user
+ * @returns {Promise<User>} A promise that resolves to the current user
+ * @throws {Error} If the API call fails or returns an invalid response
+ * @throws {Error} If the user data is invalid
  */
 export const getCurrentUser = async (): Promise<User> => {
   const response = await apiCall(`${API_BASE_URL}/auth/me`);
   const data = await response.json();
 
-  if (!response.ok) {
-    const errorData = data as ErrorResponse;
-    throw new Error(errorData.message || 'Failed to get current user');
-  }
-
   if (!isUser(data)) {
     throw new Error('Invalid user data received from API');
   }
diff --git a/app/src/api/file.ts b/app/src/api/file.ts
new file mode 100644
index 0000000..53602a8
--- /dev/null
+++ b/app/src/api/file.ts
@@ -0,0 +1,170 @@
+import { API_BASE_URL } from '@/types/authApi';
+import { apiCall } from './api';
+import {
+  FileNode,
+  isFileNode,
+  isLastOpenedFileResponse,
+  isLookupResponse,
+  isSaveFileResponse,
+  LastOpenedFileResponse,
+  LookupResponse,
+  SaveFileResponse,
+} from '@/types/fileApi';
+
+/**
+ * listFiles fetches the list of files in a workspace
+ * @param workspaceName - The name of the workspace
+ * @returns {Promise<FileNode[]>} A promise that resolves to an array of FileNode objects
+ * @throws {Error} If the API call fails or returns an invalid response
+ */
+export const listFiles = async (workspaceName: string): Promise<FileNode[]> => {
+  const response = await apiCall(
+    `${API_BASE_URL}/workspaces/${encodeURIComponent(workspaceName)}/files`
+  );
+  const data = await response.json();
+  if (!Array.isArray(data)) {
+    throw new Error('Invalid files response received from API');
+  }
+  return data.map((file) => {
+    if (!isFileNode(file)) {
+      throw new Error('Invalid file object received from API');
+    }
+    return file as FileNode;
+  });
+};
+
+/**
+ * lookupFileByName fetches the file paths that match the given filename in a workspace
+ * @param workspaceName - The name of the workspace
+ * @param filename - The name of the file to look up
+ * @returns {Promise<string[]>} A promise that resolves to an array of file paths
+ * @throws {Error} If the API call fails or returns an invalid response
+ */
+export const lookupFileByName = async (
+  workspaceName: string,
+  filename: string
+): Promise<string[]> => {
+  const response = await apiCall(
+    `${API_BASE_URL}/workspaces/${encodeURIComponent(
+      workspaceName
+    )}/files/lookup?filename=${encodeURIComponent(filename)}`
+  );
+  const data = await response.json();
+  if (!isLookupResponse(data)) {
+    throw new Error('Invalid lookup response received from API');
+  }
+  const lookupResponse = data as LookupResponse;
+  return lookupResponse.paths;
+};
+
+/**
+ * getFileContent fetches the content of a file in a workspace
+ * @param workspaceName - The name of the workspace
+ * @param filePath - The path of the file to fetch
+ * @returns {Promise<string>} A promise that resolves to the file content
+ * @throws {Error} If the API call fails or returns an invalid response
+ */
+export const getFileContent = async (
+  workspaceName: string,
+  filePath: string
+): Promise<string> => {
+  const response = await apiCall(
+    `${API_BASE_URL}/workspaces/${encodeURIComponent(
+      workspaceName
+    )}/files/${encodeURIComponent(filePath)}`
+  );
+  return response.text();
+};
+
+/**
+ * saveFile saves the content to a file in a workspace
+ * @param workspaceName - The name of the workspace
+ * @param filePath - The path of the file to save
+ * @param content - The content to save in the file
+ * @returns {Promise<SaveFileResponse>} A promise that resolves to the save file response
+ * @throws {Error} If the API call fails or returns an invalid response
+ */
+export const saveFile = async (
+  workspaceName: string,
+  filePath: string,
+  content: string
+): Promise<SaveFileResponse> => {
+  const response = await apiCall(
+    `${API_BASE_URL}/workspaces/${encodeURIComponent(
+      workspaceName
+    )}/files/${encodeURIComponent(filePath)}`,
+    {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'text/plain',
+      },
+      body: content,
+    }
+  );
+  const data = await response.json();
+  if (!isSaveFileResponse(data)) {
+    throw new Error('Invalid save file response received from API');
+  }
+  return data as SaveFileResponse;
+};
+
+/**
+ * deleteFile deletes a file in a workspace
+ * @param workspaceName - The name of the workspace
+ * @param filePath - The path of the file to delete
+ * @throws {Error} If the API call fails or returns an invalid response
+ */
+export const deleteFile = async (workspaceName: string, filePath: string) => {
+  await apiCall(
+    `${API_BASE_URL}/workspaces/${encodeURIComponent(
+      workspaceName
+    )}/files/${encodeURIComponent(filePath)}`,
+    {
+      method: 'DELETE',
+    }
+  );
+};
+
+/**
+ * getLastOpenedFile fetches the last opened file in a workspace
+ * @param workspaceName - The name of the workspace
+ * @returns {Promise<string>} A promise that resolves to the last opened file path
+ * @throws {Error} If the API call fails or returns an invalid response
+ */
+export const getLastOpenedFile = async (
+  workspaceName: string
+): Promise<string> => {
+  const response = await apiCall(
+    `${API_BASE_URL}/workspaces/${encodeURIComponent(workspaceName)}/files/last`
+  );
+  const data = await response.json();
+  if (!isLastOpenedFileResponse(data)) {
+    throw new Error('Invalid last opened file response received from API');
+  }
+  const lastOpenedFileResponse = data as LastOpenedFileResponse;
+  return lastOpenedFileResponse.lastOpenedFilePath;
+};
+
+/**
+ * updateLastOpenedFile updates the last opened file in a workspace
+ * @param workspaceName - The name of the workspace
+ * @param filePath - The path of the file to set as last opened
+ * @throws {Error} If the API call fails or returns an invalid response
+ */
+export const updateLastOpenedFile = async (
+  workspaceName: string,
+  filePath: string
+) => {
+  await apiCall(
+    `${API_BASE_URL}/workspaces/${encodeURIComponent(
+      workspaceName
+    )}/files/last`,
+    {
+      method: 'PUT',
+      headers: {
+        'Content-Type': 'application/json',
+      },
+      body: JSON.stringify({ filePath }),
+    }
+  );
+};
diff --git a/app/src/api/notes.js b/app/src/api/notes.js
index a635da9..cb8d8d4 100644
--- a/app/src/api/notes.js
+++ b/app/src/api/notes.js
@@ -22,43 +22,6 @@ export const fetchLastWorkspaceName = async () => {
   return response.json();
 };
 
-export const fetchFileList = async (workspaceName) => {
-  const response = await apiCall(
-    `${API_BASE_URL}/workspaces/${workspaceName}/files`
-  );
-  return response.json();
-};
-
-export const fetchFileContent = async (workspaceName, filePath) => {
-  const response = await apiCall(
-    `${API_BASE_URL}/workspaces/${workspaceName}/files/${filePath}`
-  );
-  return response.text();
-};
-
-export const saveFileContent = async (workspaceName, filePath, content) => {
-  const response = await apiCall(
-    `${API_BASE_URL}/workspaces/${workspaceName}/files/${filePath}`,
-    {
-      method: 'POST',
-      headers: {
-        'Content-Type': 'text/plain',
-      },
-      body: content,
-    }
-  );
-  return response.json();
-};
-
-export const deleteFile = async (workspaceName, filePath) => {
-  await apiCall(
-    `${API_BASE_URL}/workspaces/${workspaceName}/files/${filePath}`,
-    {
-      method: 'DELETE',
-    }
-  );
-};
-
 export const getWorkspace = async (workspaceName) => {
   const response = await apiCall(`${API_BASE_URL}/workspaces/${workspaceName}`);
   return response.json();
@@ -107,33 +70,6 @@ export const getFileUrl = (workspaceName, filePath) => {
   return `${API_BASE_URL}/workspaces/${workspaceName}/files/${filePath}`;
 };
 
-export const lookupFileByName = async (workspaceName, filename) => {
-  const response = await apiCall(
-    `${API_BASE_URL}/workspaces/${workspaceName}/files/lookup?filename=${encodeURIComponent(
-      filename
-    )}`
-  );
-  const data = await response.json();
-  return data.paths;
-};
-
-export const updateLastOpenedFile = async (workspaceName, filePath) => {
-  await apiCall(`${API_BASE_URL}/workspaces/${workspaceName}/files/last`, {
-    method: 'PUT',
-    headers: {
-      'Content-Type': 'application/json',
-    },
-    body: JSON.stringify({ filePath }),
-  });
-};
-
-export const getLastOpenedFile = async (workspaceName) => {
-  const response = await apiCall(
-    `${API_BASE_URL}/workspaces/${workspaceName}/files/last`
-  );
-  return response.json();
-};
-
 export const listWorkspaces = async () => {
   const response = await apiCall(`${API_BASE_URL}/workspaces`);
   return response.json();
diff --git a/app/src/types/fileApi.ts b/app/src/types/fileApi.ts
new file mode 100644
index 0000000..ffe0c49
--- /dev/null
+++ b/app/src/types/fileApi.ts
@@ -0,0 +1,73 @@
+export interface LookupResponse {
+  paths: string[];
+}
+
+export function isLookupResponse(obj: unknown): obj is LookupResponse {
+  return (
+    typeof obj === 'object' &&
+    obj !== null &&
+    'paths' in obj &&
+    Array.isArray((obj as LookupResponse).paths) &&
+    (obj as LookupResponse).paths.every((path) => typeof path === 'string')
+  );
+}
+
+export interface SaveFileResponse {
+  filePath: string;
+  size: number;
+  updatedAt: string; // ISO 8601 string representation of the date
+}
+
+export function isSaveFileResponse(obj: unknown): obj is SaveFileResponse {
+  return (
+    typeof obj === 'object' &&
+    obj !== null &&
+    'filePath' in obj &&
+    typeof (obj as SaveFileResponse).filePath === 'string' &&
+    'size' in obj &&
+    typeof (obj as SaveFileResponse).size === 'number' &&
+    'updatedAt' in obj &&
+    typeof (obj as SaveFileResponse).updatedAt === 'string'
+  );
+}
+
+export interface LastOpenedFileResponse {
+  lastOpenedFilePath: string;
+}
+
+export function isLastOpenedFileResponse(
+  obj: unknown
+): obj is LastOpenedFileResponse {
+  return (
+    typeof obj === 'object' &&
+    obj !== null &&
+    'lastOpenedFilePath' in obj &&
+    typeof (obj as LastOpenedFileResponse).lastOpenedFilePath === 'string'
+  );
+}
+
+export interface UpdateLastOpenedFileRequest {
+  filePath: string;
+}
+
+export interface FileNode {
+  id: string;
+  name: string;
+  path: string;
+  children: FileNode[];
+}
+
+export function isFileNode(obj: unknown): obj is FileNode {
+  return (
+    typeof obj === 'object' &&
+    obj !== null &&
+    'id' in obj &&
+    typeof (obj as FileNode).id === 'string' &&
+    'name' in obj &&
+    typeof (obj as FileNode).name === 'string' &&
+    'path' in obj &&
+    typeof (obj as FileNode).path === 'string' &&
+    'children' in obj &&
+    Array.isArray((obj as FileNode).children)
+  );
+}