diff --git a/src/main/kotlin/at/ac/uibk/dps/cirrina/execution/object/Action.kt b/src/main/kotlin/at/ac/uibk/dps/cirrina/execution/object/Action.kt
index 14f7fb3a..3164e1a8 100644
--- a/src/main/kotlin/at/ac/uibk/dps/cirrina/execution/object/Action.kt
+++ b/src/main/kotlin/at/ac/uibk/dps/cirrina/execution/object/Action.kt
@@ -13,6 +13,7 @@ sealed interface Action {
             description.type,
             description.mode,
             buildVariables(description.input),
+            description.output,
             buildEvents(description.emits),
           )
 
@@ -67,12 +68,13 @@ internal constructor(
   val type: String,
   val mode: InvocationMode,
   val input: List<ContextVariable>,
+  val output: List<ContextVariableReferenceDescription>,
   val emits: List<Event>,
 ) : EventRaisingAction {
   override fun raises(): List<Event> = emits
 
   override fun toString() =
-    "InvokeAction(type='$type', mode='$mode', input='$input', emits='$emits')"
+    "InvokeAction(type='$type', mode='$mode', input='$input', output='$output', emits='$emits')"
 }
 
 class MatchAction
diff --git a/src/main/kotlin/at/ac/uibk/dps/cirrina/execution/object/ActionCommand.kt b/src/main/kotlin/at/ac/uibk/dps/cirrina/execution/object/ActionCommand.kt
index ceed4349..bd0d4ed8 100644
--- a/src/main/kotlin/at/ac/uibk/dps/cirrina/execution/object/ActionCommand.kt
+++ b/src/main/kotlin/at/ac/uibk/dps/cirrina/execution/object/ActionCommand.kt
@@ -80,7 +80,10 @@ internal constructor(
 
     commandExecutionContext.coroutineScope.launch {
       runCatching { service.invoke(input) }
-        .onSuccess { emitEvents(it) }
+        .onSuccess {
+          assignServiceOutput(it, commandExecutionContext.scope.extent)
+          emitEvents(it)
+        }
         .onFailure { logger.error(it) { "service invocation failed" } }
     }
 
@@ -108,6 +111,24 @@ internal constructor(
       handler(event)
     }
   }
+
+  private fun assignServiceOutput(output: List<ContextVariable>, extent: Extent) {
+    invokeAction.output.forEach { variable ->
+      output
+        .firstOrNull { it.name == variable.reference }
+        ?.let {
+          runCatching { extent.set(variable.reference, it.value) }
+            .onFailure { e ->
+              logger.warn(e) {
+                "failed to assign service output to variable '${variable.reference}'"
+              }
+            }
+        }
+        ?: logger.warn {
+          "service output does not contain expected variable '${variable.reference}'"
+        }
+    }
+  }
 }
 
 class MatchActionCommand
diff --git a/src/main/resources/pkl/csm/csml.pkl b/src/main/resources/pkl/csm/csml.pkl
index 51f8e052..f494f516 100644
--- a/src/main/resources/pkl/csm/csml.pkl
+++ b/src/main/resources/pkl/csm/csml.pkl
@@ -96,6 +96,7 @@ class InvokeDescription extends ActionDescription {
   type: InvocationType
   mode: InvocationMode = "remote"
   input: Context
+  output: Listing<ContextVariableReferenceDescription>
   emits: Listing<EventDescription>
 }
 
@@ -131,6 +132,10 @@ class LogDescription extends ActionDescription {
   message: Expression
 }
 
+class ContextVariableReferenceDescription {
+  reference: String
+}
+
 typealias EventTopic = String(matches(Regex(#"^[a-zA-Z_]\w*$"#)))
 
 typealias EventChannel = "internal"|"external"|"peripheral"
diff --git a/src/test/kotlin/at/ac/uibk/dps/cirrina/CompleteTest.kt b/src/test/kotlin/at/ac/uibk/dps/cirrina/CompleteTest.kt
index 4f23416b..d75df9c7 100644
--- a/src/test/kotlin/at/ac/uibk/dps/cirrina/CompleteTest.kt
+++ b/src/test/kotlin/at/ac/uibk/dps/cirrina/CompleteTest.kt
@@ -27,7 +27,10 @@ class CompleteTest {
         val context = ContextInMemory()
         val server = mockHttpServer { input ->
           val v = input.firstOrNull { it.name == "v" } ?: error("variable 'v' not found")
-          listOf(ContextVariable("v", (v.value as Int) + 1))
+          listOf(
+            ContextVariable("v", (v.value as Int) + 1),
+            ContextVariable("s", (v.value + 1) * 10),
+          )
         }
 
         try {
@@ -43,6 +46,7 @@ class CompleteTest {
           assertEquals(100, context.get("v"))
           assertEquals(true, context.get("b"))
           assertEquals(true, context.get("e"))
+          assertEquals(50500, context.get("f"))
         } finally {
           server.stop(1)
         }
diff --git a/src/test/resources/pkl/complete/main.pkl b/src/test/resources/pkl/complete/main.pkl
index 224af021..7032da1b 100644
--- a/src/test/resources/pkl/complete/main.pkl
+++ b/src/test/resources/pkl/complete/main.pkl
@@ -28,10 +28,14 @@ collaborativeStateMachine {
               type = "increment"
               mode = "local"
               input { ["v"] = "x" }
+              output { new ContextVariableReferenceDescription { reference = "s" } }
               emits { new Internal { topic = "e2" } }
             }
           }
-          exit { new Assign { expression = "e = true" } }
+          exit {
+            new Assign { expression = "e = true" }
+            new Assign { expression = "f = f + s" }
+          }
           on {
             ["e2"] = new Transition {
               to = "c"
@@ -70,10 +74,13 @@ collaborativeStateMachine {
         }
         ["e"] = new Terminal { entry { new Assign { expression = "b = true" } } }
       }
-      transient { ["x"] = "0" }
+      transient {
+        ["x"] = "0"
+        ["s"] = "0"
+      }
     }
   }
-  persistent { ["b"] = "false"; ["v"] = "0"; ["e"] = "false" }
+  persistent { ["b"] = "false"; ["v"] = "0"; ["e"] = "false"; ["f"] = "0" }
 }
 instances {
   ["complete"] = new Instance { stateMachineName = "completeStateMachine" }