diff --git a/SVSim.EmulatedEntrypoint/Models/Dtos/Requests/SignupRequest.cs b/SVSim.EmulatedEntrypoint/Models/Dtos/Requests/SignupRequest.cs
new file mode 100644
index 0000000..d050adf
--- /dev/null
+++ b/SVSim.EmulatedEntrypoint/Models/Dtos/Requests/SignupRequest.cs
@@ -0,0 +1,40 @@
+using MessagePack;
+using System.Text.Json.Serialization;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Requests;
+
+/// <summary>
+/// <c>POST /tool/signup</c> request body. Spec:
+/// <c>docs/api-spec/endpoints/pre-login/tool-signup.md</c>. Client source:
+/// <c>Shadowverse_Code_2026-05-23/Cute/SignUpTask.cs</c> (LoginPostParams).
+///
+/// All fields are device telemetry; the server doesn't use them in v1 but still binds them so
+/// the request shape matches the spec exactly.
+/// </summary>
+[MessagePackObject]
+public class SignupRequest
+{
+    [JsonPropertyName("device_name")]
+    [Key("device_name")]
+    public string DeviceName { get; set; } = "";
+
+    [JsonPropertyName("client_type")]
+    [Key("client_type")]
+    public string ClientType { get; set; } = "";
+
+    [JsonPropertyName("os_version")]
+    [Key("os_version")]
+    public string OsVersion { get; set; } = "";
+
+    [JsonPropertyName("app_version")]
+    [Key("app_version")]
+    public string AppVersion { get; set; } = "";
+
+    [JsonPropertyName("resource_version")]
+    [Key("resource_version")]
+    public string ResourceVersion { get; set; } = "";
+
+    [JsonPropertyName("carrier")]
+    [Key("carrier")]
+    public string Carrier { get; set; } = "";
+}
diff --git a/SVSim.EmulatedEntrypoint/Models/Dtos/Responses/SignupResponse.cs b/SVSim.EmulatedEntrypoint/Models/Dtos/Responses/SignupResponse.cs
new file mode 100644
index 0000000..b42b94d
--- /dev/null
+++ b/SVSim.EmulatedEntrypoint/Models/Dtos/Responses/SignupResponse.cs
@@ -0,0 +1,10 @@
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Responses;
+
+/// <summary>
+/// <c>POST /tool/signup</c> response. The interesting outputs (viewer_id, short_udid, udid) all
+/// live in <c>data_headers</c>; the <c>data</c> payload is empty. <c>SignUpTask.Parse</c> never
+/// reads <c>data</c>.
+/// </summary>
+public class SignupResponse
+{
+}