diff --git a/certbot.py b/certbot.py
index f78b3b7..865dfef 100755
--- a/certbot.py
+++ b/certbot.py
@@ -12,14 +12,15 @@ from subprocess import run
 
 import certbot_config as config
 
-# Resolve include directive (non-recursive)
+# Resolve 'include' directive (non-recursive)
 def resolve_include(response, directive):
     result = []
     for index in directive['includes']:
+        # Join parsed included file to result list
         result.extend(response['config'][index]['parsed'])
     return result
         
-# Resolve all include directives (recursive)
+# Resolve all 'include' directives (recursive)
 def resolve_includes(response, directives=None):
     # Assume resolve of first file in response if not specified
     if directives is None:
@@ -29,10 +30,12 @@ def resolve_includes(response, directives=None):
     result = []
     for directive in directives:
         if 'includes' in directive:
+            # Resolve include and recursively resolve includes in included file
             result.extend(resolve_includes(response, resolve_include(response, directive)))
             continue
 
         if 'block' in directive:
+            # Recursively traverse block statement
             directive['block'] = resolve_includes(response, directive['block'])
 
         result.append(directive)
@@ -45,18 +48,23 @@ def search_directives(directives, fn, recursive=False):
 
     for directive in directives:
         if fn(directive):
+            # Append directive matched by search function to result list
             result.append(directive)
         elif recursive and 'block' in directive:
+            # Recursively search block statement
             result.extend(search_directives(directive['block'], fn, True))
 
     return result
 
 # Recursive search in directives, steered by matching functions
 def resolve_path(directives, fns):
+    # Pick the first search function in the list and perform a flat search
     results = search_directives(directives, fns[0])
     if len(results) > 0 and len(fns) > 1:
+        # A match for the first path element was found, recurse subtree to find next match
         return resolve_path(results[0]['block'], fns[1:])
     else:
+        # No further matches were found
         return results
 
 # Get all HTTP server directives
@@ -70,24 +78,31 @@ def get_vhosts(directives):
     servers = get_servers(directives)
     vhosts = []
     for server in servers:
+        # Retrieve server name directive
         server_name = search_directives(server['block'], lambda d: ('directive', 'server_name') in d.items())
         if len(server_name) == 0:
             continue
 
         for name in server_name[0]['args']:
+            # Apply server alias to vhosts list
             vhosts.append(name)
 
     return vhosts
 
+# Parse nginx.conf file with Crossplane
 response = crossplane.parse(config.nginx_config_file)
 if response['errors']:
     pprint.pprint(response['errors'])
+    sys.exit(1)
 
+# Resolve all includes (combine into to one big config tree)
 directives = resolve_includes(response)
 
+# Retrieve all virtual hostnames
 vhosts = [ name for name in get_vhosts(directives) if not name in config.ignored_domains ]
 
 if config.primary_domain in vhosts:
+    # Ensure the primary hostname comes first
     vhosts.remove(config.primary_domain)
     vhosts.insert(0, config.primary_domain)
 else:
@@ -100,10 +115,11 @@ for name in vhosts:
     print('  {}'.format(name))
 print()
 
+# Build certbot command line
 cmd = config.certbot_command
-
 for name in vhosts:
     cmd.extend(['-d', name])
+
 print('Running', ' '.join(cmd))
 print()
 run(cmd)