diff --git a/src/main/java/minevalley/core/api/Core.java b/src/main/java/minevalley/core/api/Core.java
index dad3aed..594ef85 100644
--- a/src/main/java/minevalley/core/api/Core.java
+++ b/src/main/java/minevalley/core/api/Core.java
@@ -61,6 +61,7 @@
 import org.bukkit.metadata.MetadataValue;
 import org.bukkit.metadata.Metadatable;
 import org.bukkit.plugin.java.JavaPlugin;
+import org.bukkit.scheduler.BukkitTask;
 import org.bukkit.util.Vector;
 
 import javax.annotation.Nonnull;
@@ -72,7 +73,7 @@
 import java.util.function.Consumer;
 import java.util.stream.Collectors;
 
-@SuppressWarnings("unused")
+@SuppressWarnings({"unused", "UnusedReturnValue"})
 public final class Core {
 
     private static CoreServer server;
@@ -81,56 +82,36 @@ public static JavaPlugin getInstance() {
         return server.getInstance();
     }
 
-    public static int runSyncTaskNow(Runnable runnable) {
+    @Nonnull
+    public static BukkitTask runSyncTaskNow(@Nonnull Runnable runnable) {
         return server.runSyncTaskLater(0, runnable);
     }
 
-    public static int runAsyncTaskNow(Runnable runnable) {
+    @Nonnull
+    public static BukkitTask runAsyncTaskNow(@Nonnull Runnable runnable) {
         return server.runAsyncTaskLater(0, runnable);
     }
 
-    public static int runSyncTaskLater(long delay, Runnable runnable) {
+    @Nonnull
+    public static BukkitTask runSyncTaskLater(long delay, @Nonnull Runnable runnable) {
         return server.runSyncTaskLater(delay, runnable);
     }
 
-    public static int runAsyncTaskLater(long delay, Runnable runnable) {
+    @Nonnull
+    public static BukkitTask runAsyncTaskLater(long delay, @Nonnull Runnable runnable) {
         return server.runAsyncTaskLater(delay, runnable);
     }
 
-    public static int runSyncTaskPeriodically(long delay, long period, Runnable runnable) {
+    @Nonnull
+    public static BukkitTask runSyncTaskPeriodically(long delay, long period, @Nonnull Runnable runnable) {
         return server.runSyncTaskPeriodically(delay, period, runnable);
     }
 
-    public static int runAsyncTaskPeriodically(long delay, long period, Runnable runnable) {
+    @Nonnull
+    public static BukkitTask runAsyncTaskPeriodically(long delay, long period, @Nonnull Runnable runnable) {
         return server.runAsyncTaskPeriodically(delay, period, runnable);
     }
 
-    /**
-     * Check if the task currently running.
-     * <p>
-     * A repeating task might not be running currently, but will be running in
-     * the future. A task that has finished, and does not repeat, will not be
-     * running ever again.
-     * <p>
-     * Explicitly, a task is running if there exists a thread for it, and that
-     * thread is alive.
-     *
-     * @param taskId The task to check.
-     * @return If the task is currently running.
-     */
-    public static boolean isCurrentlyRunning(int taskId) {
-        return server.isCurrentlyRunning(taskId);
-    }
-
-    /**
-     * Removes task from scheduler.
-     *
-     * @param taskId Id number of task to be removed
-     */
-    public static void cancelTask(int taskId) {
-        server.cancelTask(taskId);
-    }
-
     public static void registerListener(Class<? extends Event> cls, EventListener<? extends Event> listener) {
         server.registerListener(cls, listener);
     }
@@ -198,11 +179,12 @@ public static String getName(@Nonnull UUID uniqueId) {
      * <br>
      * <strong>Note:</strong> If no player is found, this method returns null.
      * <p>
-     *     <strong>Runtime Optimization</strong>
+     * <strong>Runtime Optimization</strong>
      *     <ul>
      *         <li>This method uses an internal cache</li>
      *         <li>If the player is online, no use of the mojang api is taken</li>
      * </p>
+     *
      * @param name name of the player
      * @return unique id as UUID
      */
diff --git a/src/main/java/minevalley/core/api/CoreServer.java b/src/main/java/minevalley/core/api/CoreServer.java
index d45960e..335edff 100644
--- a/src/main/java/minevalley/core/api/CoreServer.java
+++ b/src/main/java/minevalley/core/api/CoreServer.java
@@ -57,6 +57,7 @@
 import org.bukkit.metadata.MetadataValue;
 import org.bukkit.metadata.Metadatable;
 import org.bukkit.plugin.java.JavaPlugin;
+import org.bukkit.scheduler.BukkitTask;
 import org.bukkit.util.Vector;
 
 import java.time.DayOfWeek;
@@ -69,17 +70,17 @@ public interface CoreServer {
 
     JavaPlugin getInstance();
 
-    int runSyncTaskLater(long delay, Runnable runnable);
+    @NonNull
+    BukkitTask runSyncTaskLater(long delay, @NonNull Runnable runnable);
 
-    int runAsyncTaskLater(long delay, Runnable runnable);
+    @NonNull
+    BukkitTask runAsyncTaskLater(long delay, @NonNull Runnable runnable);
 
-    int runSyncTaskPeriodically(long delay, long period, Runnable runnable);
+    @NonNull
+    BukkitTask runSyncTaskPeriodically(long delay, long period, @NonNull Runnable runnable);
 
-    int runAsyncTaskPeriodically(long delay, long period, Runnable runnable);
-
-    boolean isCurrentlyRunning(int taskId);
-
-    void cancelTask(int taskId);
+    @NonNull
+    BukkitTask runAsyncTaskPeriodically(long delay, long period, @NonNull Runnable runnable);
 
     void registerListener(Class<? extends Event> cls, EventListener<? extends Event> listener);