diff --git a/QSB/API/AddonDataManager.cs b/QSB/API/AddonDataManager.cs
new file mode 100644
index 00000000..15731ace
--- /dev/null
+++ b/QSB/API/AddonDataManager.cs
@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using QSB.Utility;
+using UnityEngine;
+
+namespace QSB.API;
+
+public static class AddonDataManager
+{
+	private static Dictionary<string, (Type objectType, dynamic action)> _handlerDict = new();
+
+	public static void OnReceiveDataMessage(string messageType, object data)
+	{
+		DebugLog.DebugWrite($"Received data message of message type \"{messageType}\"!");
+		if (!_handlerDict.ContainsKey(messageType))
+		{
+			return;
+		}
+
+		_handlerDict[messageType].action(Convert.ChangeType(data, _handlerDict[messageType].objectType));
+	}
+
+	public static void RegisterHandler<T>(string messageType, Action<T> handler)
+	{
+		DebugLog.DebugWrite($"Registering handler for \"{messageType}\" with type of {typeof(T).Name}");
+		_handlerDict.Add(messageType, (typeof(T), handler));
+	}
+}
diff --git a/QSB/API/IQSBAPI.cs b/QSB/API/IQSBAPI.cs
new file mode 100644
index 00000000..50c33d9f
--- /dev/null
+++ b/QSB/API/IQSBAPI.cs
@@ -0,0 +1,14 @@
+using System;
+
+namespace QSB.API;
+
+internal interface IQSBAPI
+{
+	uint GetLocalPlayerID();
+
+	void SetCustomData<T>(uint playerId, string key, T data);
+	T GetCustomData<T>(uint playerId, string key);
+
+	void SendMessage<T>(string messageType, T data);
+	void RegisterHandler<T>(string messageType, Action<T> action);
+}
diff --git a/QSB/API/Messages/AddonDataMessage.cs b/QSB/API/Messages/AddonDataMessage.cs
new file mode 100644
index 00000000..792fcd0c
--- /dev/null
+++ b/QSB/API/Messages/AddonDataMessage.cs
@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Runtime.Serialization.Formatters.Binary;
+using System.Text;
+using System.Threading.Tasks;
+using QSB.Messaging;
+
+namespace QSB.API.Messages;
+public class AddonDataMessage : QSBMessage<(string messageType, byte[] data)>
+{
+	public AddonDataMessage(string messageType, object data) : base((messageType, ObjectToByteArray(data))) {}
+
+	private static byte[] ObjectToByteArray(object obj)
+	{
+		var bf = new BinaryFormatter();
+		using var ms = new MemoryStream();
+		bf.Serialize(ms, obj);
+		return ms.ToArray();
+	}
+
+	private static object ByteArrayToObject(byte[] arrBytes)
+	{
+		using var memStream = new MemoryStream();
+		var binForm = new BinaryFormatter();
+		memStream.Write(arrBytes, 0, arrBytes.Length);
+		memStream.Seek(0, SeekOrigin.Begin);
+		var obj = binForm.Deserialize(memStream);
+		return obj;
+	}
+
+	public override void OnReceiveRemote()
+	{
+		var obj = ByteArrayToObject(Data.data);
+		AddonDataManager.OnReceiveDataMessage(Data.messageType, obj);
+	}
+}
diff --git a/QSB/API/QSBAPI.cs b/QSB/API/QSBAPI.cs
new file mode 100644
index 00000000..08c83bb6
--- /dev/null
+++ b/QSB/API/QSBAPI.cs
@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using QSB.API.Messages;
+using QSB.Messaging;
+using QSB.Player;
+
+namespace QSB.API;
+
+internal class QSBAPI : IQSBAPI
+{
+	public uint GetLocalPlayerID() => QSBPlayerManager.LocalPlayerId;
+
+	public void SetCustomData<T>(uint playerId, string key, T data) => QSBPlayerManager.GetPlayer(playerId).SetCustomData(key, data);
+	public T GetCustomData<T>(uint playerId, string key) => QSBPlayerManager.GetPlayer(playerId).GetCustomData<T>(key);
+
+	public void SendMessage<T>(string messageType, T data)
+	{
+		new AddonDataMessage(messageType, data).Send();
+	}
+
+	public void RegisterHandler<T>(string messageType, Action<T> action)
+	{
+		AddonDataManager.RegisterHandler(messageType, action);
+	}
+}
diff --git a/QSB/QSB.csproj b/QSB/QSB.csproj
index 4116a8ac..3a96ae99 100644
--- a/QSB/QSB.csproj
+++ b/QSB/QSB.csproj
@@ -68,6 +68,7 @@
     </None>
   </ItemGroup>
   <ItemGroup>
+    <PackageReference Include="Microsoft.CSharp" Version="4.7.0" />
     <PackageReference Include="OuterWildsGameLibs" Version="1.1.13.457" IncludeAssets="compile" />
     <PackageReference Include="OWML" Version="2.9.3" IncludeAssets="compile" />
     <Reference Include="..\Mirror\*.dll" />
diff --git a/QSB/QSBCore.cs b/QSB/QSBCore.cs
index 67f241bb..8ab69288 100644
--- a/QSB/QSBCore.cs
+++ b/QSB/QSBCore.cs
@@ -16,6 +16,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using QSB.API;
 using UnityEngine;
 using UnityEngine.InputSystem;
 
@@ -86,6 +87,8 @@ public class QSBCore : ModBehaviour
 		"PacificEngine.OW_Randomizer",
 	};
 
+	public override object GetApi() => new QSBAPI();
+
 	private static void DetermineGameVendor()
 	{
 		var gameAssemblyTypes = typeof(AstroObject).Assembly.GetTypes();