Specify return types and async.

src/api/fetchCookie.ts

 import axios from 'axios';
 
 /**
+ * @async
  * Call for csrf cookie. This cookie is the user session identifier and
  * must be sent during the login process.
- * @returns csrf cookie
+ * @returns {string} csrf cookie
  */
 export const fetchCookie = async (): Promise<string> =>
   axios('/api/web/csrf').then((res) => res.data.token);

src/api/getRole.ts

 import axios from 'axios';
 
 /**
+ * @async
  * Asks for the current set role.
- * @returns empty if the role is not set or a name between those defined
+ * @returns {string} empty if the role is not set or a name between those defined
  * in {@see userRoles}
  */
 export const getRole = async (): Promise<string> =>

src/api/getRoles.ts

 import axios from 'axios';
 
 /**
+ * @async
  * Ask the server all the roles of an user if the user has multiple roles.
- * @returns array of roles.
+ * @returns {string[]} array of roles.
  */
 export const getRoles = async (): Promise<string[]> =>
   axios('/api/web/login/get_roles').then((res) => res.data.roles);

src/api/isAuthenticated.ts

 import axios from 'axios';
 
 /**
+ * @async
  * Ask the server if the user is authenticated.
- * @returns true or false if the user is authenticated.
+ * @returns {boolean} true or false if the user is authenticated.
  */
 export const isAuthenticated = async (): Promise<boolean> =>
   axios('/api/web/login/is_authenticated').then(

src/api/setRole.ts

 import axios from 'axios';
 
 /**
+ * @async
  * Set the role of the user in the database.
+ * @return {string} role
  */
 export const setRole = async (role: string): Promise<void> =>
   axios.post('/api/web/login/set_role', { role });