diff --git a/src/server/Elsa.Server.Api/Endpoints/Signals/Models.cs b/src/server/Elsa.Server.Api/Endpoints/Signals/Models.cs
index 4c4c4ad45..9b1374841 100644
--- a/src/server/Elsa.Server.Api/Endpoints/Signals/Models.cs
+++ b/src/server/Elsa.Server.Api/Endpoints/Signals/Models.cs
@@ -1,13 +1,74 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using Elsa.Services.Models;
 
 namespace Elsa.Server.Api.Endpoints.Signals
 {
-    public record DispatchSignalRequest(string? WorkflowInstanceId, string? CorrelationId, object? Input);
+    public record DispatchSignalRequest
+    {
+        // Need this for Swagger.
+        public DispatchSignalRequest()
+        {
+        }
+        
+        public DispatchSignalRequest(string? workflowInstanceId, string? correlationId, object? input)
+        {
+            WorkflowInstanceId = workflowInstanceId;
+            CorrelationId = correlationId;
+            Input = input;
+        }
 
-    public record DispatchSignalResponse(ICollection<PendingWorkflow> StartedWorkflows);
+        public string? WorkflowInstanceId { get; init; }
+        public string? CorrelationId { get; init; }
+        public object? Input { get; init; }
+    }
 
-    public record ExecuteSignalRequest(string? WorkflowInstanceId, string? CorrelationId, object? Input);
+    public record DispatchSignalResponse
+    {
+        // Need this for Swagger.
+        public DispatchSignalResponse()
+        {
+        }
+        
+        public DispatchSignalResponse(ICollection<PendingWorkflow> startedWorkflows)
+        {
+            StartedWorkflows = startedWorkflows;
+        }
 
-    public record ExecuteSignalResponse(ICollection<StartedWorkflow> StartedWorkflows);
+        public ICollection<PendingWorkflow> StartedWorkflows { get; init; } = default!;
+    }
+
+    public record ExecuteSignalRequest
+    {
+        // Need this for Swagger.
+        public ExecuteSignalRequest()
+        {
+        }
+        
+        public ExecuteSignalRequest(string? workflowInstanceId, string? correlationId, object? input)
+        {
+            WorkflowInstanceId = workflowInstanceId;
+            CorrelationId = correlationId;
+            Input = input;
+        }
+        
+        public string? WorkflowInstanceId { get; init; }
+        public string? CorrelationId { get; init; }
+        public object? Input { get; init; }
+    }
+
+    public record ExecuteSignalResponse
+    {
+        // Need this for Swagger.
+        public ExecuteSignalResponse()
+        {
+        }
+
+        public ExecuteSignalResponse(ICollection<StartedWorkflow> startedWorkflows)
+        {
+            StartedWorkflows = startedWorkflows;
+        }
+        
+        public ICollection<StartedWorkflow> StartedWorkflows { get; init; } = new List<StartedWorkflow>();
+    }
 }
\ No newline at end of file