diff --git a/PasswordKeeper.BusinessLogic/Users.cs b/PasswordKeeper.BusinessLogic/Users.cs
index 8e30c14..dabfda5 100644
--- a/PasswordKeeper.BusinessLogic/Users.cs
+++ b/PasswordKeeper.BusinessLogic/Users.cs
@@ -10,7 +10,7 @@ namespace PasswordKeeper.BusinessLogic;
 public class Users(PasswordKeeper.DataAccess.Users users)
 {
     /// <inheritdoc cref="PasswordKeeper.DataAccess.Users.UpsertUser"/>
-    public async Task<bool> UpsertUser(UserDto userDto)
+    public async Task<UserDto?> UpsertUser(UserDto userDto)
     {
         return await users.UpsertUser(userDto);
     }
diff --git a/PasswordKeeper.DataAccess/Users.cs b/PasswordKeeper.DataAccess/Users.cs
index a1de3cb..17c749b 100644
--- a/PasswordKeeper.DataAccess/Users.cs
+++ b/PasswordKeeper.DataAccess/Users.cs
@@ -30,8 +30,8 @@ public class Users(IDbContextFactory<Entities> dbContextFactory, IMapper mapper)
     /// Upserts a user. If the user doesn't exist, inserts it, otherwise updates it.
     /// </summary>
     /// <param name="userDto">The user to upsert.</param>
-    /// <returns><c>true</c> if the user was upserted successfully, otherwise <c>false</c>.</returns>
-    public async Task<bool> UpsertUser(UserDto userDto)
+    /// <returns>The upserted user data or <c>null</c> if the operation failed.</returns>
+    public async Task<UserDto?> UpsertUser(UserDto userDto)
     {
         await using var context = await dbContextFactory.CreateDbContextAsync();
         
@@ -49,6 +49,6 @@ public async Task<bool> UpsertUser(UserDto userDto)
         
         await context.SaveChangesAsync();
         
-        return true;
+        return mapper.Map<UserDto>(user);
     }
 }
\ No newline at end of file
diff --git a/PasswordKeeperServer/Controllers/AuthenticationController.cs b/PasswordKeeperServer/Controllers/AuthenticationController.cs
index fbbe293..e2b9bca 100644
--- a/PasswordKeeperServer/Controllers/AuthenticationController.cs
+++ b/PasswordKeeperServer/Controllers/AuthenticationController.cs
@@ -1,4 +1,5 @@
 using System.IdentityModel.Tokens.Jwt;
+using System.Security.Authentication;
 using System.Security.Claims;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
@@ -47,9 +48,9 @@ public async Task<IActionResult> Login([FromBody] UserLogin user)
                 PasswordSalt = Convert.ToBase64String(salt!),
             };
 
-            await users.UpsertUser(userDto);
+            userDto = await users.UpsertUser(userDto);
             
-            var token = GenerateJwtToken(user.Username);
+            var token = GenerateJwtToken(user.Username, userDto.Id);
             return Ok(new { token, });
         }
 
@@ -59,7 +60,7 @@ public async Task<IActionResult> Login([FromBody] UserLogin user)
             if (Users.VerifyPassword(user.Password, userDto.PasswordHash,
                     Convert.FromBase64String(userDto.PasswordSalt)))
             {
-                var token = GenerateJwtToken(user.Username);
+                var token = GenerateJwtToken(user.Username, userDto.Id);
                 return Ok(new { token, });
             }
         }
@@ -77,17 +78,35 @@ public IActionResult TestUnauthorized()
         return Ok();
     }
     
+    /// <summary>
+    /// Gets the logged-in user's ID.
+    /// </summary>
+    /// <returns>The logged-in user's ID, or -1 if the claim containing the user ID is not found.</returns>
+    long GetLoggedUserId()
+    {
+        var claim = User.Claims.FirstOrDefault(c => c.Type == ClaimTypes.NameIdentifier && long.TryParse(c.Value, out _));
+        
+        if (long.TryParse(claim?.Value, out var result))
+        {
+            return result;
+        }
+        
+        return -1;
+    }
+    
     /// <summary>
     /// Generates a JWT token for the given username.
     /// </summary>
     /// <param name="username">The username to generate the JWT token for.</param>
+    /// <param name="userId">The user ID to generate the JWT token for.</param>
     /// <returns>The JWT token.</returns>
-    private string GenerateJwtToken(string username)
+    private string GenerateJwtToken(string username, long userId)
     {
         var claims = new[]
         {
             new Claim(JwtRegisteredClaimNames.Sub, username),
             new Claim(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString()),
+            new Claim(JwtRegisteredClaimNames.NameId, userId.ToString()),
         };
         
         var key = new SymmetricSecurityKey(Program.JwtKey);
diff --git a/PasswordKeeperServer/Program.cs b/PasswordKeeperServer/Program.cs
index 388ca05..0bebffe 100644
--- a/PasswordKeeperServer/Program.cs
+++ b/PasswordKeeperServer/Program.cs
@@ -3,6 +3,7 @@
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.IdentityModel.Tokens;
+using Microsoft.OpenApi;
 using MySql.Data.MySqlClient;
 using PasswordKeeper.BusinessLogic;
 using PasswordKeeper.DAO;
@@ -70,7 +71,11 @@ public static void Main(string[] args)
         builder.Services.AddAutoMapper(typeof(AutoMapperProfile));
         
         // Learn more about configuring OpenAPI at https://aka.ms/aspnet/openapi
-        builder.Services.AddOpenApi();
+        builder.Services.AddOpenApi("v3",options =>
+        {
+            options.ShouldInclude = operation => operation.HttpMethod != null;
+            options.OpenApiVersion = OpenApiSpecVersion.OpenApi3_0;
+        });
 
         var app = builder.Build();