diff --git a/Communication.md b/Communication.md
index 20be467..f3dbb25 100644
--- a/Communication.md
+++ b/Communication.md
@@ -35,8 +35,11 @@ Commands from _execution thread_ to _listening thread_:
 
 - **done** - notifying of finished job. Requires 2 message frames:
     - `job_id` - identifier of finished job
-    - `result` - response result, one of "OK" and "FAILED"
-    - `message` - non-empty error description if result was "FAILED"
+    - `result` - response result, possible values below
+        - OK - everything ok
+        - FAILED - execution failed and cannot be reassigned to another worker (due to error in configuration for example)
+        - INTERNAL_ERROR - execution failed due to internal worker error, but other worker possibly can execute this without error
+    - `message` - non-empty error description if result was not "OK"
 
 
 ### Progress callback