diff --git a/pisa-btc/apps/__init__.py b/pisa-btc/apps/__init__.py
index 41def5a..bf87110 100644
--- a/pisa-btc/apps/__init__.py
+++ b/pisa-btc/apps/__init__.py
@@ -1,2 +1,2 @@
 PISA_API_SERVER = 'localhost'
-PISA_API_PORT = 2222
+PISA_API_PORT = 2222
\ No newline at end of file
diff --git a/pisa-btc/apps/messages.py b/pisa-btc/apps/messages.py
index 39c83d9..b57d1ed 100644
--- a/pisa-btc/apps/messages.py
+++ b/pisa-btc/apps/messages.py
@@ -1 +1 @@
-wrong_txid = "You should provide the 16 MSB (in base58 hex) of the txid you'd like to be monitored."
\ No newline at end of file
+wrong_txid = "You should provide the 16 MSB (in hex) of the txid you'd like to be monitored."
\ No newline at end of file
diff --git a/pisa-btc/apps/pisa-cli.py b/pisa-btc/apps/pisa-cli.py
index 0782c8b..2cd0817 100644
--- a/pisa-btc/apps/pisa-cli.py
+++ b/pisa-btc/apps/pisa-cli.py
@@ -3,25 +3,22 @@ from getopt import getopt
 from sys import argv
 from apps import PISA_API_SERVER, PISA_API_PORT
 import apps.messages as msg
-from base58 import b58decode
+import re
 
-
-commands = ['register_tx']
+commands = ['add_appointment']
 
 
 def check_txid_format(txid):
     if len(txid) != 32:
         raise Exception("txid does not matches the expected size (16-byte / 32 hex chars). " + msg.wrong_txid)
-    try:
-        b58decode(txid)
-    except ValueError:
-        raise Exception("The provided txid is not in base58. " + msg.wrong_txid)
+
+    return re.search(r'^[0-9A-Fa-f]+$', txid) is not None
 
 
 def show_usage():
     print("usage: python pisa-cli.py argument [additional_arguments]."
           "\nArguments:"
-          "\nregister_tx half_txid: \tregisters a txid to be monitored by PISA using the 16 MSB of the txid (in hex)."
+          "\nadd_appointment appointment: \tregisters a json formatted appointment "
           "\nhelp: \t\tshows this message.")
 
 
@@ -36,17 +33,20 @@ if __name__ == '__main__':
 
     if command in commands:
 
-        if command == 'register_tx':
+        if command in commands:
             if len(args) != 2:
                 raise Exception("txid missing. " + msg.wrong_txid)
 
             arg = args[1]
-            check_txid_format(arg)
+            valid_locator = check_txid_format(arg)
 
-        conn = Client((PISA_API_SERVER, PISA_API_PORT))
+            if valid_locator:
+                conn = Client((PISA_API_SERVER, PISA_API_PORT))
 
-        # Argv could be undefined, but we only have one command for now so safe
-        conn.send((command, arg))
+                # Argv could be undefined, but we only have one command so it's safe for now
+                conn.send((command, arg))
+            else:
+                raise ValueError("The provided locator is not valid. " + msg.wrong_txid)
 
     else:
         show_usage()
diff --git a/pisa-btc/pisa/api.py b/pisa-btc/pisa/api.py
index c69e415..c5e3f05 100644
--- a/pisa-btc/pisa/api.py
+++ b/pisa-btc/pisa/api.py
@@ -35,7 +35,7 @@ def manage_request(conn, remote_addr, remote_port, inspector, watcher, debug, lo
                     command, arg = msg
 
                     if command == "add_appointment":
-                        appointment = inspector.inspect(msg, debug)
+                        appointment = inspector.inspect(arg, debug)
                         if appointment:
                             appointment_added = watcher.add_appointment(appointment, debug, logging)