diff --git a/clay/gp.py b/clay/gp.py
index 08bb805..ec77045 100644
--- a/clay/gp.py
+++ b/clay/gp.py
@@ -5,7 +5,10 @@ Google Play Music integration via gmusicapi.
 # pylint: disable=too-many-arguments
 # pylint: disable=too-many-instance-attributes
 # pylint: disable=too-many-return-statements
+# pylint: disable=protected-access
 from __future__ import print_function
+import os
+import json
 from threading import Thread, Lock
 from uuid import UUID
 
@@ -415,7 +418,12 @@ class GP(object):
 
     def __init__(self):
         assert self.__class__.instance is None, 'Can be created only once!'
+        self.is_debug = os.getenv('CLAY_DEBUG')
         self.mobile_client = Mobileclient()
+        if self.is_debug:
+            self.mobile_client._make_call = self._make_call_proxy(self.mobile_client._make_call)
+            self.debug_file = open('/tmp/clay-api-log.json', 'w')
+            self._last_call_index = 0
         self.cached_tracks = None
         self.cached_playlists = None
 
@@ -433,6 +441,26 @@ class GP(object):
 
         return cls.instance
 
+    def _make_call_proxy(self, func):
+        """
+        Return a function that wraps *fn* and logs args & return values.
+        """
+        def _make_call(protocol, *args, **kwargs):
+            """
+            Wrapper function.
+            """
+            result = func(protocol, *args, **kwargs)
+            self._last_call_index += 1
+            call_index = self._last_call_index
+            self.debug_file.write(json.dumps([
+                call_index,
+                protocol.__name__, args, kwargs,
+                result
+            ]) + '\n')
+            self.debug_file.flush()
+            return result
+        return _make_call
+
     def invalidate_caches(self):
         """
         Clear cached tracks & playlists.
diff --git a/clay/meta.py b/clay/meta.py
index 33c1a6a..56f0278 100644
--- a/clay/meta.py
+++ b/clay/meta.py
@@ -7,7 +7,7 @@ except ImportError:
     codename = None
 
 APP_NAME = 'Clay Player'
-VERSION = '0.5.3'
+VERSION = '0.5.4'
 if codename is not None:
     VERSION += '-' + codename(separator='-', id=VERSION)
 USER_AGENT = ' '.join([