diff --git a/src/mcp/Server.zig b/src/mcp/Server.zig
index e3ef8097..ffba7396 100644
--- a/src/mcp/Server.zig
+++ b/src/mcp/Server.zig
@@ -87,7 +87,7 @@ pub fn sendResult(self: *Self, id: std.json.Value, result: anytype) !void {
 }
 
 pub fn sendError(self: *Self, id: std.json.Value, code: protocol.ErrorCode, message: []const u8) !void {
-    try self.sendResponse(.{
+    try self.sendResponse(protocol.Response{
         .id = id,
         .@"error" = protocol.Error{
             .code = @intFromEnum(code),
@@ -114,7 +114,7 @@ test "MCP.Server - Integration: synchronous smoke test" {
 
     try router.processRequests(server, &in_reader);
 
-    try testing.expectJson(.{ .id = 1 }, out_alloc.writer.buffered());
+    try testing.expectJson(.{ .jsonrpc = "2.0", .id = 1 }, out_alloc.writer.buffered());
 }
 
 test "MCP.Server - Integration: ping request returns an empty result" {
@@ -135,5 +135,5 @@ test "MCP.Server - Integration: ping request returns an empty result" {
 
     try router.processRequests(server, &in_reader);
 
-    try testing.expectJson(.{ .id = "ping-1", .result = .{} }, out_alloc.writer.buffered());
+    try testing.expectJson(.{ .jsonrpc = "2.0", .id = "ping-1", .result = .{} }, out_alloc.writer.buffered());
 }
diff --git a/src/mcp/router.zig b/src/mcp/router.zig
index 1bc02624..38b2e206 100644
--- a/src/mcp/router.zig
+++ b/src/mcp/router.zig
@@ -120,7 +120,7 @@ test "MCP.router - handleMessage - synchronous unit tests" {
         \\{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test-client","version":"1.0.0"}}}
     );
     try testing.expectJson(
-        \\{ "id": 1, "result": { "capabilities": { "tools": {} } } }
+        \\{ "jsonrpc": "2.0", "id": 1, "result": { "capabilities": { "tools": {} } } }
     , out_alloc.writer.buffered());
     out_alloc.writer.end = 0;
 
@@ -128,14 +128,14 @@ test "MCP.router - handleMessage - synchronous unit tests" {
     try handleMessage(server, aa,
         \\{"jsonrpc":"2.0","id":2,"method":"ping"}
     );
-    try testing.expectJson(.{ .id = 2, .result = .{} }, out_alloc.writer.buffered());
+    try testing.expectJson(.{ .jsonrpc = "2.0", .id = 2, .result = .{} }, out_alloc.writer.buffered());
     out_alloc.writer.end = 0;
 
     // 3. Tools list
     try handleMessage(server, aa,
         \\{"jsonrpc":"2.0","id":3,"method":"tools/list"}
     );
-    try testing.expectJson(.{ .id = 3 }, out_alloc.writer.buffered());
+    try testing.expectJson(.{ .jsonrpc = "2.0", .id = 3 }, out_alloc.writer.buffered());
     try testing.expect(std.mem.indexOf(u8, out_alloc.writer.buffered(), "\"name\":\"goto\"") != null);
     out_alloc.writer.end = 0;
 
@@ -143,7 +143,7 @@ test "MCP.router - handleMessage - synchronous unit tests" {
     try handleMessage(server, aa,
         \\{"jsonrpc":"2.0","id":4,"method":"unknown_method"}
     );
-    try testing.expectJson(.{ .id = 4, .@"error" = .{ .code = -32601 } }, out_alloc.writer.buffered());
+    try testing.expectJson(.{ .jsonrpc = "2.0", .id = 4, .@"error" = .{ .code = -32601 } }, out_alloc.writer.buffered());
     out_alloc.writer.end = 0;
 
     // 5. Parse error
@@ -152,6 +152,6 @@ test "MCP.router - handleMessage - synchronous unit tests" {
         defer filter.deinit();
 
         try handleMessage(server, aa, "invalid json");
-        try testing.expectJson("{\"id\": null, \"error\": {\"code\": -32700}}", out_alloc.writer.buffered());
+        try testing.expectJson("{\"jsonrpc\": \"2.0\", \"id\": null, \"error\": {\"code\": -32700}}", out_alloc.writer.buffered());
     }
 }