diff --git a/3.component_model.md b/3.component_model.md
index 86fae55..6020e98 100644
--- a/3.component_model.md
+++ b/3.component_model.md
@@ -135,6 +135,9 @@ A Server is used for long-running, scalable workloads that have a network endpoi
  - A Server is daemonized. A runtime MUST attempt to restart replicas that exit regardless of error code.
  - A Server has a network endpoint with an automatically assigned virtual IP address (VIP) and DNS name addressable within the network scope to which the component belongs.
 
+> If a Server does not provide at least one `port` on at least one `container`, implementations SHOULD emit an error.
+
+
 ##### Singleton Server
 Workload type name: `core.oam.dev/v1alpha1.SingletonServer`
 
@@ -143,6 +146,8 @@ A Singleton Server is a special case of the Server workload type that is limited
  - A Singleton Server is daemonized. A runtime MUST attempt to restart the singleton replica if it exits regardless of error code.
  - A Singleton Server has a network endpoint with an automatically assigned virtual IP address (VIP) and DNS name addressable within the network scope to which the component belongs.
 
+> If a Singleton Server does not provide at least one `port` on at least one `container`, implementations SHOULD emit an error.
+
 ##### Worker
 Workload type name: `core.oam.dev/v1alpha1.Worker`
 
@@ -151,6 +156,8 @@ A worker is used for long-running, scalable workloads that do not have a service
  - An application operator can increase or decrease the number of worker replicas by applying and configuring traits when available.
  - A worker is daemonized. A runtime MUST attempt to restart replicas that exit regardless of error code.
 
+> If a Worker declares a `port` on any `container`, this SHOULD result in a validation error.
+
 ##### Singleton Worker
 Workload type name: `core.oam.dev/v1alpha1.SingletonWorker`
 
@@ -158,6 +165,7 @@ A singleton worker is a special case of the worker workload type that is limited
  - Defines a container runtime where at most one replica of the same container may be run at a time.  
  - A singleton worker is daemonized. A runtime MUST attempt to restart the singleton replica if it exits regardless of error code.
 
+> If a Singleton Worker declares a `port` on any `container`, this SHOULD result in a validation error.
 
 ##### Task
 Workload type name: `core.oam.dev/v1alpha1.Task`