diff --git a/deployment_manifest_schema.json b/deployment_manifest_schema.json
new file mode 100644
index 0000000..ae6e57b
--- /dev/null
+++ b/deployment_manifest_schema.json
@@ -0,0 +1,59 @@
+{
+  "$id": "https://restate.dev/deployment.manifest.json",
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "type": "object",
+  "title": "Deployment",
+  "description": "Restate deployment manifest",
+  "properties": {
+    "protocolMode": {
+      "title": "ProtocolMode",
+      "enum": ["BIDI_STREAM", "REQUEST_RESPONSE"]
+    },
+    "minProtocolVersion": {
+      "type": "integer",
+      "minimum": 0
+    },
+    "maxProtocolVersion": {
+      "type": "integer",
+      "maximum": 0
+    },
+    "components": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "title": "Component",
+        "properties": {
+          "fullyQualifiedComponentName": {
+            "type": "string",
+            "pattern": "^[a-zA-Z]+[a-zA-Z0-9._-]*$"
+          },
+          "componentType": {
+            "title": "ComponentType",
+            "enum": ["VIRTUAL_OBJECT", "SERVICE"]
+          },
+          "handlers": {
+            "type": "array",
+            "items": {
+              "type": "object",
+              "title": "Handler",
+              "properties": {
+                "name": {
+                  "type": "string",
+                  "pattern": "^[a-zA-Z]+[a-zA-Z0-9_-]*$"
+                },
+                "inputSchema": {},
+                "outputSchema": {}
+              },
+              "required": [ "name" ],
+              "additionalProperties": false
+            }
+          }
+        },
+        "required": [ "fullyQualifiedComponentName","componentType", "handlers" ],
+        "additionalProperties": false
+      }
+    }
+  },
+  "required": [ "minProtocolVersion", "maxProtocolVersion", "components" ],
+  "additionalProperties": false
+}
\ No newline at end of file
diff --git a/dev/restate/service/protocol.proto b/dev/restate/service/protocol.proto
index 97b7f46..8131bfb 100644
--- a/dev/restate/service/protocol.proto
+++ b/dev/restate/service/protocol.proto
@@ -41,6 +41,9 @@ message StartMessage {
   bool partial_state = 5;
 
   repeated Header headers = 6;
+
+  // If this invocation has a key associated (e.g. for objects and workflows), then this key is filled in. Empty otherwise.
+  string key = 7;
 }
 
 // Type: 0x0000 + 1
@@ -200,6 +203,9 @@ message InvokeEntryMessage {
 
   repeated Header headers = 4;
 
+  // If this invocation has a key associated (e.g. for objects and workflows), then this key is filled in. Empty otherwise.
+  string key = 5;
+
   oneof result {
     bytes value = 14;
     Failure failure = 15;
@@ -222,6 +228,9 @@ message BackgroundInvokeEntryMessage {
   uint64 invoke_time = 4;
 
   repeated Header headers = 5;
+
+  // If this invocation has a key associated (e.g. for objects and workflows), then this key is filled in. Empty otherwise.
+  string key = 6;
 }
 
 // Completable: Yes