diff --git a/crates/rmcp/src/model.rs b/crates/rmcp/src/model.rs
index e0f0bb24..3c86fbbd 100644
--- a/crates/rmcp/src/model.rs
+++ b/crates/rmcp/src/model.rs
@@ -2045,6 +2045,7 @@ impl RequestParamsMeta for CancelTaskParams {
 pub type CancelTaskParam = CancelTaskParams;
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
 #[serde(rename_all = "camelCase")]
+#[serde(deny_unknown_fields)]
 #[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
 pub struct GetTaskInfoResult {
     #[serde(skip_serializing_if = "Option::is_none")]
@@ -2130,11 +2131,11 @@ ts_union!(
     | UnsubscribeRequest
     | CallToolRequest
     | ListToolsRequest
-    | CustomRequest
     | GetTaskInfoRequest
     | ListTasksRequest
     | GetTaskResultRequest
-    | CancelTaskRequest;
+    | CancelTaskRequest
+    | CustomRequest;
 );
 
 impl ClientRequest {
@@ -2153,11 +2154,11 @@ impl ClientRequest {
             ClientRequest::UnsubscribeRequest(r) => r.method.as_str(),
             ClientRequest::CallToolRequest(r) => r.method.as_str(),
             ClientRequest::ListToolsRequest(r) => r.method.as_str(),
-            ClientRequest::CustomRequest(r) => r.method.as_str(),
             ClientRequest::GetTaskInfoRequest(r) => r.method.as_str(),
             ClientRequest::ListTasksRequest(r) => r.method.as_str(),
             ClientRequest::GetTaskResultRequest(r) => r.method.as_str(),
             ClientRequest::CancelTaskRequest(r) => r.method.as_str(),
+            ClientRequest::CustomRequest(r) => r.method.as_str(),
         }
     }
 }
@@ -2222,11 +2223,11 @@ ts_union!(
     | ListToolsResult
     | CreateElicitationResult
     | EmptyResult
-    | CustomResult
     | CreateTaskResult
     | ListTasksResult
     | GetTaskInfoResult
     | TaskResult
+    | CustomResult
     ;
 );
 
diff --git a/crates/rmcp/tests/test_message_schema/client_json_rpc_message_schema.json b/crates/rmcp/tests/test_message_schema/client_json_rpc_message_schema.json
index e0d90fa8..6e45c5f1 100644
--- a/crates/rmcp/tests/test_message_schema/client_json_rpc_message_schema.json
+++ b/crates/rmcp/tests/test_message_schema/client_json_rpc_message_schema.json
@@ -862,9 +862,6 @@
         {
           "$ref": "#/definitions/RequestOptionalParam4"
         },
-        {
-          "$ref": "#/definitions/CustomRequest"
-        },
         {
           "$ref": "#/definitions/Request9"
         },
@@ -876,6 +873,9 @@
         },
         {
           "$ref": "#/definitions/Request11"
+        },
+        {
+          "$ref": "#/definitions/CustomRequest"
         }
       ],
       "required": [
diff --git a/crates/rmcp/tests/test_message_schema/client_json_rpc_message_schema_current.json b/crates/rmcp/tests/test_message_schema/client_json_rpc_message_schema_current.json
index e0d90fa8..6e45c5f1 100644
--- a/crates/rmcp/tests/test_message_schema/client_json_rpc_message_schema_current.json
+++ b/crates/rmcp/tests/test_message_schema/client_json_rpc_message_schema_current.json
@@ -862,9 +862,6 @@
         {
           "$ref": "#/definitions/RequestOptionalParam4"
         },
-        {
-          "$ref": "#/definitions/CustomRequest"
-        },
         {
           "$ref": "#/definitions/Request9"
         },
@@ -876,6 +873,9 @@
         },
         {
           "$ref": "#/definitions/Request11"
+        },
+        {
+          "$ref": "#/definitions/CustomRequest"
         }
       ],
       "required": [
diff --git a/crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json b/crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json
index b848d4ee..f1596857 100644
--- a/crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json
+++ b/crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json
@@ -857,7 +857,8 @@
             }
           ]
         }
-      }
+      },
+      "additionalProperties": false
     },
     "Icon": {
       "description": "A URL pointing to an icon resource or a base64-encoded data URI.\n\nClients that support rendering icons MUST support at least the following MIME types:\n- image/png - PNG images (safe, universal compatibility)\n- image/jpeg (and image/jpg) - JPEG images (safe, universal compatibility)\n\nClients that support rendering icons SHOULD also support:\n- image/svg+xml - SVG images (scalable but requires security precautions)\n- image/webp - WebP images (modern, efficient format)",
@@ -2452,9 +2453,6 @@
         {
           "$ref": "#/definitions/EmptyObject"
         },
-        {
-          "$ref": "#/definitions/CustomResult"
-        },
         {
           "$ref": "#/definitions/CreateTaskResult"
         },
@@ -2466,6 +2464,9 @@
         },
         {
           "$ref": "#/definitions/TaskResult"
+        },
+        {
+          "$ref": "#/definitions/CustomResult"
         }
       ]
     },
diff --git a/crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json b/crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json
index b848d4ee..f1596857 100644
--- a/crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json
+++ b/crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json
@@ -857,7 +857,8 @@
             }
           ]
         }
-      }
+      },
+      "additionalProperties": false
     },
     "Icon": {
       "description": "A URL pointing to an icon resource or a base64-encoded data URI.\n\nClients that support rendering icons MUST support at least the following MIME types:\n- image/png - PNG images (safe, universal compatibility)\n- image/jpeg (and image/jpg) - JPEG images (safe, universal compatibility)\n\nClients that support rendering icons SHOULD also support:\n- image/svg+xml - SVG images (scalable but requires security precautions)\n- image/webp - WebP images (modern, efficient format)",
@@ -2452,9 +2453,6 @@
         {
           "$ref": "#/definitions/EmptyObject"
         },
-        {
-          "$ref": "#/definitions/CustomResult"
-        },
         {
           "$ref": "#/definitions/CreateTaskResult"
         },
@@ -2466,6 +2464,9 @@
         },
         {
           "$ref": "#/definitions/TaskResult"
+        },
+        {
+          "$ref": "#/definitions/CustomResult"
         }
       ]
     },