diff --git a/src/protocol/generate_protocol.py b/src/protocol/generate_protocol.py
index a5a8259..5cbc339 100644
--- a/src/protocol/generate_protocol.py
+++ b/src/protocol/generate_protocol.py
@@ -5,6 +5,10 @@ text = ''
 varint_max_size = 5
 indent_count = 0
 
+# Print to stderr
+def warn(value, *args, sep='', end='\n', flush=False):
+    print(value, *args, sep=sep, end=end, file=sys.stderr, flush=flush)
+
 def indent():
     global indent_count
     indent_count += 1
@@ -32,37 +36,74 @@ def extract_array_type(type):
 def extract_array_count(type):
     if '[' in type and ']' in type:
         return int(type[type.find('[')+1:type.rfind(']')])
-    return 1
+    return None
 
-def resolve_type(aliases, type):
-    type_no_array = type.rstrip('_')
-    if type_no_array in aliases:
-        return aliases[type_no_array]
-    return type
+def get_type_info(types, typename, aliases={}):
+    name = extract_array_type(typename)
 
-def get_type_size(type):
-    global varint_max_size
-    count = extract_array_count(type)
-    type  = extract_array_type(type)
+    alias_name = None
+    if aliases and name in aliases:
+        alias_name = name
+        name = aliases[name]
 
-    # TODO: encode type sizes in Hjson data
-    if type == 'varint':
-        return varint_max_size
-    elif type == 'int64' or type == 'uint64' or type == 'double' or type == 'position':
-        return 8
-    elif type == 'int32' or type == 'uint32' or type == 'float':
-        return 4
-    elif type == 'int16' or type == 'uint16':
-        return 2
-    elif type == 'int8' or type == 'uint8' or type == 'byte' or type == 'bool':
-        return 1
-    elif type == 'string':
-        return count
-    elif type == 'uuid':
-        return 16
+    if not name in types:
+        warn('WARNING: Type name "{}" is not a known type or alias.'.format(name))
+        return {
+            type: name
+        }
+
+    tp = types[name]
+
+    if 'alias' in tp:
+        alias = tp['alias']
+        tp = get_type_info(types, tp['alias']).copy()
+        tp['alias'] = alias
+        if tp['generic'] == True:
+            tp['type'] = name
+    
+    if alias_name:
+        tp = tp.copy()
+        tp['alias'] = name
+        tp['type'] = alias_name
+    
+    # types without a 'type' value use their own name (e.g. double, float)
+    if not 'type' in tp:
+        tp['type'] = name
+
+    return tp
+
+def resolve_type(types, typename, aliases={}):
+    tp = get_type_info(types, typename, aliases)
+    if 'type' in tp:
+        return tp['type']
     else:
-        print(type)
-        assert False
+        return typename
+
+def get_type_size(types, typename, aliases={}):
+    global varint_max_size
+
+    tp = get_type_info(types, typename, aliases)
+
+    if not 'size' in tp:
+        if 'alias' in tp:
+            return get_type_size(types, tp['alias'])
+        else:
+            warn('ERROR: Non-alias type "{}" does not have "size" field.'.format(typename))
+            exit(1)
+
+    size = tp['size']
+
+    if size == 'count':
+        size = extract_array_count(typename)
+    
+    if not size:
+        warn('ERROR: Cannot get size for type "{}"'.format(typename))
+        exit(1)
+
+
+    #print("get_type_size: {} -> {}".format(typename, size))
+
+    return int(size)
 
 def print_enum(name, dict, primitive = 'int32_t'):
     add_text('enum class {} : {}', name, primitive)
@@ -73,21 +114,27 @@ def print_enum(name, dict, primitive = 'int32_t'):
     unindent()
     add_text('}};')
 
-def get_rw_func(primitiveType, aliasedType, read):
-    prefix = 'Read' if read else 'Write'
-    if aliasedType == 'varint':
-        if primitiveType == 'int32_t':
-            return '{}VarInt'.format(prefix)    
-        else:
-            return '{}VarInt<{}>'.format(prefix, primitiveType)
-    elif aliasedType == 'string':
-        return '{}String'.format(prefix)
-    elif aliasedType == 'position':
-        return '{}Position'.format(prefix)
-    else:
-        return '{}<{}>'.format(prefix, primitiveType)
+def get_rw_func(types, typename, read, aliases={}):
+    method = 'Read' if read else 'Write'
 
-def print_messages(list, global_aliases, primitives):
+    #print("{}: ({}, {})".format(method, typename, read))
+
+    tp = get_type_info(types, typename, aliases)
+
+    if 'method' in tp:
+        method += tp['method']
+
+    generic = 'generic' in tp and tp['generic']
+    alias = 'alias' in tp 
+
+    if (generic and alias) or not 'method' in tp:
+        method += '<' + tp['type'] + '>'
+    
+    #print('{} -> {}'.format(typename, method))
+
+    return method
+    
+def print_messages(list, types):
     global text
     for state, direction_list in list.items():
         add_text('namespace {}', state.capitalize())
@@ -97,10 +144,8 @@ def print_messages(list, global_aliases, primitives):
             serverbound = direction == 'serverbound'
             for message_name, message in messages.items():
                 
-                # global and local aliases
-                aliases = global_aliases.copy()
-
                 # add any local aliases
+                aliases = {}
                 if 'aliases' in message:
                     for alias in message['aliases']:
                         aliases[alias] = message['aliases'][alias]
@@ -108,8 +153,8 @@ def print_messages(list, global_aliases, primitives):
                 global varint_max_size
                 size  = varint_max_size # Packet Length
                 size += varint_max_size # Packet Id
-                for name, type in message['vars'].items():
-                    size += get_type_size(resolve_type(aliases, type))
+                for name, typename in message['vars'].items():
+                    size += get_type_size(types, typename, aliases)
 
                 struct_name = '{}{}'.format(direction.capitalize(), message_name)
                 add_text('struct {}', struct_name)
@@ -124,7 +169,7 @@ def print_messages(list, global_aliases, primitives):
                     for enum in message['enums']:
                         if enum in aliases:
                             # lookup enum primitive type from aliases
-                            prim = resolve_type(primitives, aliases[enum])
+                            prim = resolve_type(types, aliases[enum])
                             print_enum(enum, message['enums'][enum], prim)
                         else:
                             print_enum(enum, message['enums'][enum])
@@ -133,8 +178,11 @@ def print_messages(list, global_aliases, primitives):
                     add_text('{}(PacketReader& reader)', struct_name)
                     add_text('{{')
                     indent()
-                    for name, type in message['vars'].items():
-                        add_text('{} = reader.{}();', name, get_rw_func(resolve_type(primitives, extract_array_type(type)), resolve_type(aliases, extract_array_type(type)), True))
+                    for name, typename in message['vars'].items():
+                        add_text('{} = reader.{}();',
+                            name,
+                            get_rw_func(types, typename, True, aliases)
+                        )
                     unindent()
                     add_text('}}')
                     newline()
@@ -144,15 +192,18 @@ def print_messages(list, global_aliases, primitives):
                     indent()
                     add_text('NetworkMessage msg(MaxSize);')
                     add_text('msg.WriteVarInt(PacketId);')
-                    for name, type in message['vars'].items():
-                        add_text('msg.{}({});', get_rw_func(resolve_type(primitives, extract_array_type(type)), resolve_type(aliases, extract_array_type(type)), False), name)
+                    for name, typename in message['vars'].items():
+                        add_text('msg.{}({});', 
+                            get_rw_func(types, typename, False, aliases),
+                            name
+                        )
                     add_text('msg.Finalize();')
                     add_text('return msg;')
                     unindent()
                     add_text('}}')
 
-                for name, type in message['vars'].items():
-                    resolved_type = resolve_type(primitives, extract_array_type(type))
+                for name, typename in message['vars'].items():
+                    resolved_type = resolve_type(types, extract_array_type(typename), aliases)
                     if not serverbound and resolved_type == 'std::string':
                         add_text('const {}& {};', resolved_type, name)
                     else:
@@ -229,8 +280,8 @@ def print_protocol():
 
         print_messages(
             message_scheme['messages'],
-            message_scheme['types']['aliases'],
-            message_scheme['types']['primitives'])
+            message_scheme['types']
+        )
 
         newline()
 
diff --git a/src/protocol/protocol.hjson b/src/protocol/protocol.hjson
index 14951ba..e5f8304 100644
--- a/src/protocol/protocol.hjson
+++ b/src/protocol/protocol.hjson
@@ -1,29 +1,53 @@
 {
-    types :
+    types:
     {
-        aliases :
-        {
-            ProtocolState : varint
+        varint: {
+            type: int32_t
+            size: 5
+            method: VarInt
+            generic: true
         }
 
-        primitives :
-        {
-            varint : int32_t
-            string : std::string
-            uuid   : MinecraftUUID
-            position: BlockPos
-
-            uint64 : uint64_t
-            int64  : int64_t
-            uint32 : uint32_t
-            int32  : int32_t
-            uint16 : uint16_t
-            int16  : int16_t
-            uint8  : uint8_t
-            int8   : int8_t
-            byte   : uint8_t
-            bool   : uint8_t
+        ProtocolState: {
+            alias: varint
         }
+
+        string: {
+            type: std::string
+            method: String
+            size: count
+        }
+
+        uuid: {
+            type: MinecraftUUID
+            size: 16
+        }
+
+        position: {
+            type: BlockPos
+            size: 8
+            method: Position
+        }
+
+        uint64: {type: 'uint64_t', size: 8}
+        int64: {type: 'int64_t', size: 8}
+
+        uint32: {type: 'uint32_t', size: 4}
+        int32: {type: 'int32_t', size: 4}
+
+        uint16: {type: 'uint16_t', size: 2}
+        int16: {type: 'int16_t', size: 2}
+
+        uint8: {type: 'uint8_t', size: 1}
+        int8: {type: 'int8_t', size: 1}
+
+        byte: {type: 'uint8_t', size: 1}
+
+        bool: {type: 'bool', size: 1}
+
+        float: {size: 4}
+        double: {size: 8}
+
     }
 
     states :