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 d63caa37..08eaa7f5 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
@@ -34,6 +34,7 @@ sealed interface Action {
             description.type,
             description.mode,
             buildVariables(description.input),
+            description.output,
             buildEvents(description.raises),
           )
 
@@ -88,6 +89,7 @@ internal constructor(
   val type: String,
   val mode: InvocationMode,
   val input: List<ContextVariable>,
+  val output: List<ContextVariableReferenceDescription>,
   val raises: List<Event>,
 ) : EventRaisingAction {
   override fun raises(): List<Event> = raises
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 9eb4c1c1..b3ca54fe 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 { raiseEvents(it) }
+        .onSuccess {
+          assignServiceOutput(it, commandExecutionContext.scope.extent)
+          raiseEvents(it)
+        }
         .onFailure { logger.error(it) { "service invocation failed" } }
     }
 
@@ -96,6 +99,24 @@ internal constructor(
   private fun prepareInput(extent: Extent): List<ContextVariable> =
     invokeAction.input.map { it.evaluate(extent) }
 
+  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}'"
+        }
+    }
+  }
+
   private fun raiseEvents(output: List<ContextVariable>) {
     invokeAction.raises.forEach { eventTemplate ->
       val event = eventTemplate.copy(data = output)
diff --git a/src/main/resources/pkl/csm/csml.pkl b/src/main/resources/pkl/csm/csml.pkl
index 57275ad5..f413203e 100644
--- a/src/main/resources/pkl/csm/csml.pkl
+++ b/src/main/resources/pkl/csm/csml.pkl
@@ -99,6 +99,7 @@ class InvokeDescription extends ActionDescription {
   type: InvocationType
   mode: InvocationMode = "remote"
   input: Context
+  output: Listing<ContextVariableReferenceDescription>
   raises: Listing<EventDescription>
 }
 
@@ -134,6 +135,10 @@ class LogDescription extends ActionDescription {
   message: Expression
 }
 
+class ContextVariableReferenceDescription {
+  reference: String
+}
+
 typealias EventTopic = String(matches(Regex(#"^[a-zA-Z_]\w*$"#)))
 
 typealias EventChannel = "internal"|"external"|"global"|"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 cea46fbe..8365a561 100644
--- a/src/test/kotlin/at/ac/uibk/dps/cirrina/CompleteTest.kt
+++ b/src/test/kotlin/at/ac/uibk/dps/cirrina/CompleteTest.kt
@@ -29,7 +29,10 @@ 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 {
@@ -45,6 +48,7 @@ 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/completeStateMachine.pkl b/src/test/resources/pkl/complete/completeStateMachine.pkl
index 9865716b..bec7a420 100644
--- a/src/test/resources/pkl/complete/completeStateMachine.pkl
+++ b/src/test/resources/pkl/complete/completeStateMachine.pkl
@@ -18,11 +18,13 @@ sm = new csml.StateMachine {
           type = "increment"
           mode = "local"
           input { ["v"] = "x" }
+          output { new csml.ContextVariableReferenceDescription { reference = "s" } }
           raises { new csml.Internal { topic = "e2" } }
         }
       }
       exit {
         new csml.Eval { expression = "e = true" }
+        new csml.Eval { expression = "f = f + s" }
       }
       on {
         ["e2"] = new csml.Transition { to = "c"; do { new csml.Eval { expression = "x = $v" } } }
@@ -52,5 +54,8 @@ sm = new csml.StateMachine {
     }
     ["e"] = new csml.Terminal { entry { new csml.Eval { expression = "b = true" } } }
   }
-  transient { ["x"] = "0" }
+  transient {
+    ["x"] = "0"
+    ["s"] = "0"
+  }
 }
\ No newline at end of file
diff --git a/src/test/resources/pkl/complete/main.pkl b/src/test/resources/pkl/complete/main.pkl
index 297cc3a3..32b71978 100644
--- a/src/test/resources/pkl/complete/main.pkl
+++ b/src/test/resources/pkl/complete/main.pkl
@@ -6,7 +6,7 @@ collaborativeStateMachine {
   stateMachines {
     ["completeStateMachine"] = completeStateMachine.sm
   }
-  persistent { ["b"] = "false"; ["v"] = "0"; ["e"] = "false" }
+  persistent { ["b"] = "false"; ["v"] = "0"; ["e"] = "false"; ["f"] = "0" }
 }
 instances {
   ["complete"] = "completeStateMachine"