diff --git a/chat.proto b/chat.proto
new file mode 100644
index 0000000..ed94500
--- /dev/null
+++ b/chat.proto
@@ -0,0 +1,81 @@
+syntax = "proto3";
+
+package chat;
+
+//    _______                   ________    |
+//   |ooooooo|      ____       | __  __ |   |
+//   |[]+++[]|     [____]      |/  \/  \|   |
+//   |+ ___ +|     ]()()[      |\__/\__/|   |
+//   |:|   |:|   ___\__/___    |[][][][]|   |
+//   |:|___|:|  |__|    |__|   |++++++++|   |
+//   |[]===[]|   |_|_/\_|_|    | ______ |   |
+// _ ||||||||| _ | | __ | | __ ||______|| __|
+//   |_______|   |_|[::]|_|    |________|   \
+//               \_|_||_|_/               jro\
+//                 |_||_|                     \
+//                _|_||_|_                     \
+//        ____   |___||___|                     \
+//       /  __\          ____                    \
+//       \( oo          (___ \                    \
+//       _\_o/           oo~)/
+//      / \|/ \         _\-_/_
+//     / / __\ \___    / \|/  \
+//     \ \|   |__/_)  / / .- \ \
+//      \/_)  |       \ \ .  /_/
+//       ||___|        \/___(_/
+//       | | |          | |  |
+//       | | |          | |  |
+//       |_|_|          |_|__|
+//       [__)_)        (_(___]
+// Credit: https://www.asciiart.eu/
+
+option go_package = "github.com/overmindtech/sdp-go;sdp";
+
+// this is based on https://platform.openai.com/docs/api-reference/messages/object
+message ChatMessage {
+    repeated Content content = 1;
+    repeated Attachments attachments = 2;
+}
+
+message Content {
+    string type = 1;
+    oneof content {
+        Text text = 2;
+        ImageFile imageFile = 3;
+        ImageURL imageURL = 4;
+    }
+}
+
+message ImageFile {
+    string fileID = 1;
+    string detail = 2;
+}
+
+message ImageURL {
+    string url = 1;
+    string detail = 2;
+}
+
+message Text {
+    string text = 1;
+}
+
+message Attachments {
+    string fileID = 1;
+    repeated Tools tools = 2;
+}
+
+message Tools {
+    oneof tool {
+        CodeInterpreter codeInterpreter = 1;
+        FileSearch fileSearch = 2;
+    }
+}
+
+message CodeInterpreter {
+    string Type = 1;
+}
+
+message FileSearch {
+    string Type = 1;
+}
diff --git a/gateway.proto b/gateway.proto
index 8df5ae8..bbe1aa4 100644
--- a/gateway.proto
+++ b/gateway.proto
@@ -2,6 +2,7 @@ syntax = "proto3";
 
 package gateway;
 
+import "chat.proto";
 import "items.proto";
 import "responses.proto";
 import "google/protobuf/duration.proto";
@@ -60,6 +61,7 @@ message GatewayRequest {
         // CancelLoadBookmark cancelLoadBookmark = ??;
         // // undo the loading of a Bookmark
         // UndoLoadBookmark undoLoadBookmark = ??;
+        SendChatMessage sendChatMessage = 16;
     }
 
     optional google.protobuf.Duration minStatusInterval = 2; // Minimum time between status updates. Setting this value too low can result in too many status messages
@@ -90,6 +92,8 @@ message GatewayResponse {
         BookmarkLoadResult bookmarkLoadResult = 16;
 
         QueryStatus queryStatus = 17; // Status of requested queries
+
+        ChatMessageResult chatMessageResult = 18;
     }
 }
 
@@ -205,3 +209,22 @@ message SnapshotLoadResult {
     // a correlation ID to match up requests and responses. this field returns the contents of the request's msgID
     bytes msgID = 4;
 }
+
+message SendChatMessage {
+    // a correlation ID to match up requests and responses. set this to a value unique per connection
+    bytes msgID = 1;
+    // The message to create
+    string message = 2;
+    // we can in future only use ChatMessage instead of 'string message'
+    chat.ChatMessage chatMessage = 3;
+}
+
+message ChatMessageResult {
+    // a correlation ID to match up requests and responses. this field returns the contents of the request's msgID
+    bytes msgID = 1;
+    bool success = 2;
+    string errorMessage = 3;
+    string message = 4;
+    // we can in future only use ChatMessage instead of 'string message'
+    chat.ChatMessage chatMessage = 5;
+}