diff --git a/README.md b/README.md
index b21dfd7..76f580b 100755
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@ An example of usage is demonstrated below:
 ```python
 import planimation_api as api
 result = api.pddl_visualise("domain.pddl", "problem.pddl", "ap.pddl", "mp4")
-print(result) // display the name of received file
+print(result) # display the name of the received file or an error message
 ```
 
 ### Command Line Utility
@@ -39,5 +39,5 @@ The API should be considered to be in a very alpha phase at the moment. It's not
 ### Thanks
 The first version of Planimation API is developed by Changyuan Liu, Lingfeng Qiang, Mengyi Fan, Xinzhe Li and Zhaoqi Fang under Nir Lipovetzky's guidance.
 
-[//]: # 
+[//]: #
    [here]:<https://planimation.planning.domains/>
diff --git a/planimation.py b/planimation.py
index d247f92..414a0dd 100644
--- a/planimation.py
+++ b/planimation.py
@@ -26,22 +26,22 @@
 				if vfg.endswith('.vfg'):
 					i+=1
 					downloadtype = sys.argv[i].strip()
-					
+
 					if downloadtype!='png' and downloadtype!='webm' and downloadtype!='gif' and downloadtype!='mp4':
-						print("invalid download type")
+						print("Error: desired output format is not supported; only png, gif, webm and mp4 are supported")
 						exit(1)
 					else:
-						print(vfg)
-						print(downloadtype)
-						api.vfg_visualise(vfg,downloadtype)
+						#print(vfg)
+						#print(downloadtype)
+						print(api.vfg_visualise(vfg,downloadtype))
 						exit(0)
 				else:
-					print("Invalid vfg file type")
+					print("Error: incorrect input format; input should be in vfg format")
 					exit(1)
 			else:
-				print("Invalid argument entered for submitVFG")
+				print("Error: incorrect number of arguments entered for submitVFG")
 				exit(1)
-		# check submitPlan function 		
+		# check submitPlan function
 		elif sys.argv[i] == "submitPDDL":
 			i+=1
 			if len(sys.argv) == 6:
@@ -54,20 +54,20 @@
 					i+=1
 					downloadtype = sys.argv[i].strip()
 					if downloadtype!='png' and downloadtype!='webm' and downloadtype!='gif' and downloadtype!='mp4' and downloadtype!='vfg':
-						print("invalid download type")
+						print("Error: desired output format is not supported; only vfg, png, gif, webm and mp4 are supported")
 						exit(1)
 					else:
-						api.pddl_visualise(domainFile,problemFile,animationFile,downloadtype)
+						print(api.pddl_visualise(domainFile,problemFile,animationFile,downloadtype))
 						exit(0)
 
 				else:
-					print("invalid input for pddls,please check your pddl files")
+					print("Error: incorrect input format; all input files should be in pddl format")
 					exit(1)
 
 			else:
-				print("Invalid argument numbers entered for submitPlan")
+				print("Error: incorrect number of arguments numbers entered for submitPDDL")
 				exit(1)
 
 		else:
-			print("no such argument input!!!")
-			exit(1)
\ No newline at end of file
+			print("Error: no such command " + "'" + sys.argv[1] + "'")
+			exit(1)
diff --git a/planimation_api.py b/planimation_api.py
index 730941a..31f7cf8 100644
--- a/planimation_api.py
+++ b/planimation_api.py
@@ -1,6 +1,7 @@
 import requests
 from datetime import datetime
 import re
+import json
 
 # To be changed once deployed on actural server
 pddl_url = "http://127.0.0.1:8000/upload/(?P<filename>[^/]+)$"
@@ -35,7 +36,11 @@ def pddl_visualise(domain_file, problem_file, animation_profile, output_format):
     animation = read_file(animation_profile)
     files = ("domain", (None, domain)), ("problem", (None, problem)), ("animation", (None, animation)), \
             ("fileType", (None, output_format))
+    print("Waiting for response...")
     r = requests.post(pddl_url, files=files)
+    if "message" in r.text:
+        message = json.loads(r.text)
+        return message['message']
     if output_format == "png":
         output_format = "zip"
     output_name = "planimation " + datetime.now().strftime("%Y-%m-%d_%X.") + output_format
@@ -55,7 +60,11 @@ def vfg_visualise(vfg_file, output_format):
         return None
     vfg = read_file(vfg_file)
     files = ('vfg', (None, vfg)), ('fileType', (None, output_format))
+    print("Waiting for response...")
     r = requests.post(vfg_url, files=files)
+    if "message" in r.text:
+        message = json.loads(r.text)
+        return message['message']
     if output_format == "png":
         output_format = "zip"
     output_name = "planimation " + datetime.now().strftime("%Y-%m-%d_%X.") + output_format