diff --git a/example-plugin/maubot.yaml b/example-plugin/maubot.yaml
index c173d37..0665091 100644
--- a/example-plugin/maubot.yaml
+++ b/example-plugin/maubot.yaml
@@ -1,6 +1,9 @@
 # This is an example maubot plugin definition file.
 # All plugins must include a file like this named "maubot.yaml" in their root directory.
 
+# Target maubot version
+maubot: 0.1.0
+
 # The unique ID for the plugin. Java package naming style. (i.e. use your own domain, not xyz.maubot)
 id: xyz.maubot.example
 
@@ -24,6 +27,9 @@ modules:
 # The main class must extend maubot.Plugin
 main_class: HelloWorldBot
 
+# Whether or not instances need a database
+database: false
+
 #  Extra files that the upcoming build tool should include in the mbp file.
 #extra_files:
 #- base-config.yaml
diff --git a/maubot/__init__.py b/maubot/__init__.py
index c3148ae..3e2ffac 100644
--- a/maubot/__init__.py
+++ b/maubot/__init__.py
@@ -1,3 +1,2 @@
 from .plugin_base import Plugin
-from .command_spec import CommandSpec, Command, PassiveCommand, Argument
 from .matrix import MaubotMatrixClient as Client, MaubotMessageEvent as MessageEvent
diff --git a/maubot/cli/commands/build.py b/maubot/cli/commands/build.py
index 699e36f..5e67b0b 100644
--- a/maubot/cli/commands/build.py
+++ b/maubot/cli/commands/build.py
@@ -122,6 +122,8 @@ def upload_plugin(output: Union[str, IO], server: str) -> None:
 @click.option("-s", "--server", help="Server to upload built plugin to")
 def build(path: str, output: str, upload: bool, server: str) -> None:
     meta = read_meta(path)
+    if not meta:
+        return
     if output or not upload:
         output = read_output_path(output, meta)
         if not output:
diff --git a/maubot/client.py b/maubot/client.py
index 5b91d8c..1ec6d4f 100644
--- a/maubot/client.py
+++ b/maubot/client.py
@@ -55,7 +55,7 @@ class Client:
                                          token=self.access_token, client_session=self.http_client,
                                          log=self.log, loop=self.loop, store=self.db_instance)
         if self.autojoin:
-            self.client.add_event_handler(self._handle_invite, EventType.ROOM_MEMBER)
+            self.client.add_event_handler(EventType.ROOM_MEMBER, self._handle_invite)
 
     async def start(self, try_n: Optional[int] = 0) -> None:
         try:
@@ -260,9 +260,9 @@ class Client:
         if value == self.db_instance.autojoin:
             return
         if value:
-            self.client.add_event_handler(self._handle_invite, EventType.ROOM_MEMBER)
+            self.client.add_event_handler(EventType.ROOM_MEMBER, self._handle_invite)
         else:
-            self.client.remove_event_handler(self._handle_invite, EventType.ROOM_MEMBER)
+            self.client.remove_event_handler(EventType.ROOM_MEMBER, self._handle_invite)
         self.db_instance.autojoin = value
 
     @property
diff --git a/maubot/command_spec.py b/maubot/command_spec.py
deleted file mode 100644
index 55c3279..0000000
--- a/maubot/command_spec.py
+++ /dev/null
@@ -1,155 +0,0 @@
-# maubot - A plugin-based Matrix bot system.
-# Copyright (C) 2018 Tulir Asokan
-#
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Affero General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Affero General Public License for more details.
-#
-# You should have received a copy of the GNU Affero General Public License
-# along with this program.  If not, see <https://www.gnu.org/licenses/>.
-from typing import List, Dict, Pattern, Union, Tuple, Optional, Any
-from attr import dataclass
-import re
-
-from mautrix.types import MessageEvent, MatchedCommand, MatchedPassiveCommand
-from mautrix.client.api.types.util import SerializableAttrs
-
-
-@dataclass
-class Argument(SerializableAttrs['Argument']):
-    matches: str
-    required: bool = False
-    description: str = None
-
-
-@dataclass
-class Command(SerializableAttrs['Command']):
-    syntax: str
-    arguments: Dict[str, Argument] = {}
-    description: str = None
-
-
-@dataclass
-class PassiveCommand(SerializableAttrs['PassiveCommand']):
-    name: str
-    matches: str
-    match_against: str
-    match_event: MessageEvent = None
-
-
-class ParsedCommand:
-    name: str
-    is_passive: bool
-    arguments: List[str]
-    starts_with: str
-    matches: Pattern
-    match_against: str
-    match_event: MessageEvent
-
-    def __init__(self, command: Union[PassiveCommand, Command]) -> None:
-        if isinstance(command, PassiveCommand):
-            self._init_passive(command)
-        elif isinstance(command, Command):
-            self._init_active(command)
-        else:
-            raise ValueError("Command parameter must be a Command or a PassiveCommand.")
-
-    def _init_passive(self, command: PassiveCommand) -> None:
-        self.name = command.name
-        self.is_passive = True
-        self.match_against = command.match_against
-        self.matches = re.compile(command.matches, re.UNICODE)
-        self.match_event = command.match_event
-
-    def _init_active(self, command: Command) -> None:
-        self.name = command.syntax
-        self.is_passive = False
-        self.arguments = []
-
-        regex_builder = []
-        sw_builder = []
-        argument_encountered = False
-
-        for word in command.syntax.split(" "):
-            arg = command.arguments.get(word, None)
-            if arg is not None and len(word) > 0:
-                argument_encountered = True
-                regex = f"({arg.matches})"
-                if not arg.required:
-                    regex += "?"
-                self.arguments.append(word)
-                regex_builder.append(regex)
-            else:
-                if not argument_encountered:
-                    sw_builder.append(word)
-                regex_builder.append(re.escape(word))
-        self.starts_with = "!" + " ".join(sw_builder)
-        self.matches = re.compile("^!" + " ".join(regex_builder) + "$", re.UNICODE)
-        self.match_against = "body"
-
-    def match(self, evt: MessageEvent) -> bool:
-        return self._match_passive(evt) if self.is_passive else self._match_active(evt)
-
-    @staticmethod
-    def _parse_key(key: str) -> Tuple[str, Optional[str]]:
-        if '.' not in key:
-            return key, None
-        key, next_key = key.split('.', 1)
-        if len(key) > 0 and key[0] == "[":
-            end_index = next_key.index("]")
-            key = key[1:] + "." + next_key[:end_index]
-            next_key = next_key[end_index + 2:] if len(next_key) > end_index + 1 else None
-        return key, next_key
-
-    @classmethod
-    def _recursive_get(cls, data: Any, key: str) -> Any:
-        if not data:
-            return None
-        key, next_key = cls._parse_key(key)
-        if next_key is not None:
-            return cls._recursive_get(data[key], next_key)
-        return data[key]
-
-    def _match_passive(self, evt: MessageEvent) -> bool:
-        try:
-            match_against = self._recursive_get(evt.content, self.match_against)
-        except KeyError:
-            match_against = None
-        match_against = match_against or evt.content.body
-        matches = [[match.string[match.start():match.end()]] + list(match.groups())
-                   for match in self.matches.finditer(match_against)]
-        if not matches:
-            return False
-        if evt.unsigned.passive_command is None:
-            evt.unsigned.passive_command = {}
-        evt.unsigned.passive_command[self.name] = MatchedPassiveCommand(captured=matches)
-        return True
-
-    def _match_active(self, evt: MessageEvent) -> bool:
-        if not evt.content.body.startswith(self.starts_with):
-            return False
-        match = self.matches.match(evt.content.body)
-        if not match:
-            return False
-        evt.content.command = MatchedCommand(matched=self.name,
-                                             arguments=dict(zip(self.arguments, match.groups())))
-        return True
-
-
-@dataclass
-class CommandSpec(SerializableAttrs['CommandSpec']):
-    commands: List[Command] = []
-    passive_commands: List[PassiveCommand] = []
-
-    def __add__(self, other: 'CommandSpec') -> 'CommandSpec':
-        return CommandSpec(commands=self.commands + other.commands,
-                           passive_commands=self.passive_commands + other.passive_commands)
-
-    def parse(self) -> List[ParsedCommand]:
-        return [ParsedCommand(command) for command in self.commands + self.passive_commands]
diff --git a/maubot/config.py b/maubot/config.py
index ab3e080..b36a5c5 100644
--- a/maubot/config.py
+++ b/maubot/config.py
@@ -29,7 +29,8 @@ class Config(BaseFileConfig):
         return "".join(random.choice(string.ascii_lowercase + string.digits) for _ in range(64))
 
     def do_update(self, helper: ConfigUpdateHelper) -> None:
-        base, copy, _ = helper
+        base = helper.base
+        copy = helper.copy
         copy("database")
         copy("plugin_directories.upload")
         copy("plugin_directories.load")
diff --git a/maubot/handlers/__init__.py b/maubot/handlers/__init__.py
new file mode 100644
index 0000000..be2d03e
--- /dev/null
+++ b/maubot/handlers/__init__.py
@@ -0,0 +1 @@
+from . import event, command
diff --git a/maubot/handlers/command.py b/maubot/handlers/command.py
new file mode 100644
index 0000000..28f3c78
--- /dev/null
+++ b/maubot/handlers/command.py
@@ -0,0 +1,359 @@
+# maubot - A plugin-based Matrix bot system.
+# Copyright (C) 2018 Tulir Asokan
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from typing import (Union, Callable, Sequence, Pattern, Awaitable, NewType, Optional, Any, List,
+                    Dict, Tuple, Set)
+from abc import ABC, abstractmethod
+import asyncio
+import functools
+import inspect
+import re
+
+from mautrix.types import MessageType, EventType
+
+from ..matrix import MaubotMessageEvent
+from . import event
+
+PrefixType = Optional[Union[str, Callable[[], str]]]
+AliasesType = Union[List[str], Tuple[str, ...], Set[str], Callable[[str], bool]]
+CommandHandlerFunc = NewType("CommandHandlerFunc",
+                             Callable[[MaubotMessageEvent, Any], Awaitable[Any]])
+CommandHandlerDecorator = NewType("CommandHandlerDecorator",
+                                  Callable[[Union['CommandHandler', CommandHandlerFunc]],
+                                           'CommandHandler'])
+PassiveCommandHandlerDecorator = NewType("PassiveCommandHandlerDecorator",
+                                         Callable[[CommandHandlerFunc], CommandHandlerFunc])
+
+
+def _split_in_two(val: str, split_by: str) -> List[str]:
+    return val.split(split_by, 1) if split_by in val else [val, ""]
+
+
+class CommandHandler:
+    def __init__(self, func: CommandHandlerFunc) -> None:
+        self.__mb_func__: CommandHandlerFunc = func
+        self.__mb_parent__: CommandHandler = None
+        self.__mb_subcommands__: List[CommandHandler] = []
+        self.__mb_arguments__: List[Argument] = []
+        self.__mb_help__: str = None
+        self.__mb_get_name__: Callable[[], str] = None
+        self.__mb_is_command_match__: Callable[[Any, str], bool] = self.__command_match_unset
+        self.__mb_require_subcommand__: bool = True
+        self.__mb_arg_fallthrough__: bool = True
+        self.__mb_event_handler__: bool = True
+        self.__mb_event_type__: EventType = EventType.ROOM_MESSAGE
+        self.__class_instance: Any = None
+
+    @staticmethod
+    def __command_match_unset(self, val: str) -> str:
+        raise NotImplementedError("Hmm")
+
+    async def __call__(self, evt: MaubotMessageEvent, *, _existing_args: Dict[str, Any] = None,
+                       remaining_val: str = None) -> Any:
+        if evt.sender == evt.client.mxid:
+            return
+        if remaining_val is None:
+            if not evt.content.body or evt.content.body[0] != "!":
+                return
+            command, remaining_val = _split_in_two(evt.content.body[1:], " ")
+            if not self.__mb_is_command_match__(self, command):
+                return
+        call_args: Dict[str, Any] = {**_existing_args} if _existing_args else {}
+
+        if not self.__mb_arg_fallthrough__ and len(self.__mb_subcommands__) > 0:
+            ok, res = await self.__call_subcommand__(evt, call_args, remaining_val)
+            if ok:
+                return res
+
+        ok, remaining_val = await self.__parse_args__(evt, call_args, remaining_val)
+        if not ok:
+            return
+        elif self.__mb_arg_fallthrough__ and len(self.__mb_subcommands__) > 0:
+            ok, res = await self.__call_subcommand__(evt, call_args, remaining_val)
+            if ok:
+                return res
+            elif self.__mb_require_subcommand__:
+                await evt.reply(self.__mb_full_help__)
+                return
+
+        if self.__class_instance:
+            return await self.__mb_func__(self.__class_instance, evt, **call_args)
+        return await self.__mb_func__(evt, **call_args)
+
+    async def __call_subcommand__(self, evt: MaubotMessageEvent, call_args: Dict[str, Any],
+                                  remaining_val: str) -> Tuple[bool, Any]:
+        command, remaining_val = _split_in_two(remaining_val.strip(), " ")
+        for subcommand in self.__mb_subcommands__:
+            if subcommand.__mb_is_command_match__(subcommand.__class_instance, command):
+                return True, await subcommand(evt, _existing_args=call_args,
+                                              remaining_val=remaining_val)
+        return False, None
+
+    async def __parse_args__(self, evt: MaubotMessageEvent, call_args: Dict[str, Any],
+                             remaining_val: str) -> Tuple[bool, str]:
+        for arg in self.__mb_arguments__:
+            try:
+                remaining_val, call_args[arg.name] = arg.match(remaining_val.strip())
+                if arg.required and not call_args[arg.name]:
+                    raise ValueError("Argument required")
+            except ArgumentSyntaxError as e:
+                await evt.reply(e.message + (f"\n{self.__mb_usage__}" if e.show_usage else ""))
+                return False, remaining_val
+            except ValueError as e:
+                await evt.reply(self.__mb_usage__)
+                return False, remaining_val
+        return True, remaining_val
+
+    def __get__(self, instance, instancetype):
+        self.__class_instance = instance
+        return self
+
+    @property
+    def __mb_full_help__(self) -> str:
+        usage = self.__mb_usage_without_subcommands__ + "\n\n"
+        usage += "\n".join(cmd.__mb_usage_inline__ for cmd in self.__mb_subcommands__)
+        return usage
+
+    @property
+    def __mb_usage_args__(self) -> str:
+        arg_usage = " ".join(f"<{arg.label}>" if arg.required else f"[{arg.label}]"
+                             for arg in self.__mb_arguments__)
+        if self.__mb_subcommands__ and self.__mb_arg_fallthrough__:
+            arg_usage += " " + self.__mb_usage_subcommand__
+        return arg_usage
+
+    @property
+    def __mb_usage_subcommand__(self) -> str:
+        return f"<subcommand> [...]"
+
+    @property
+    def __mb_name__(self) -> str:
+        return self.__mb_get_name__(self.__class_instance)
+
+    @property
+    def __mb_prefix__(self) -> str:
+        if self.__mb_parent__:
+            return f"{self.__mb_parent__.__mb_prefix__} {self.__mb_name__}"
+        return f"!{self.__mb_name__}"
+
+    @property
+    def __mb_usage_inline__(self) -> str:
+        if not self.__mb_arg_fallthrough__:
+            return (f"* {self.__mb_name__} {self.__mb_usage_args__} - {self.__mb_help__}\n"
+                    f"* {self.__mb_name__} {self.__mb_usage_subcommand__}")
+        return f"* {self.__mb_name__} {self.__mb_usage_args__} - {self.__mb_help__}"
+
+    @property
+    def __mb_subcommands_list__(self) -> str:
+        return f"**Subcommands:** {', '.join(self.__mb_subcommands__.keys())}"
+
+    @property
+    def __mb_usage_without_subcommands__(self) -> str:
+        if not self.__mb_arg_fallthrough__:
+            return (f"**Usage:** {self.__mb_prefix__} {self.__mb_usage_args__}"
+                    f" _OR_ {self.__mb_usage_subcommand__}")
+        return f"**Usage:** {self.__mb_prefix__} {self.__mb_usage_args__}"
+
+    @property
+    def __mb_usage__(self) -> str:
+        if len(self.__mb_subcommands__) > 0:
+            return f"{self.__mb_usage_without_subcommands__}  \n{self.__mb_subcommands_list__}"
+        return self.__mb_usage_without_subcommands__
+
+    def subcommand(self, name: PrefixType = None, *, help: str = None, aliases: AliasesType = None,
+                   required_subcommand: bool = True, arg_fallthrough: bool = True,
+                   ) -> CommandHandlerDecorator:
+        def decorator(func: Union[CommandHandler, CommandHandlerFunc]) -> CommandHandler:
+            if not isinstance(func, CommandHandler):
+                func = CommandHandler(func)
+            new(name, help=help, aliases=aliases, require_subcommand=required_subcommand,
+                arg_fallthrough=arg_fallthrough)(func)
+            func.__mb_parent__ = self
+            func.__mb_event_handler__ = False
+            self.__mb_subcommands__.append(func)
+            return func
+
+        return decorator
+
+
+def new(name: PrefixType = None, *, help: str = None, aliases: AliasesType = None,
+        event_type: EventType = EventType.ROOM_MESSAGE, require_subcommand: bool = True,
+        arg_fallthrough: bool = True) -> CommandHandlerDecorator:
+    def decorator(func: Union[CommandHandler, CommandHandlerFunc]) -> CommandHandler:
+        if not isinstance(func, CommandHandler):
+            func = CommandHandler(func)
+        func.__mb_help__ = help
+        if name:
+            if callable(name):
+                if len(inspect.getfullargspec(name).args) == 0:
+                    func.__mb_get_name__ = lambda self: name()
+                else:
+                    func.__mb_get_name__ = name
+            else:
+                func.__mb_get_name__ = lambda self: name
+        else:
+            func.__mb_get_name__ = lambda self: func.__name__
+        if callable(aliases):
+            if len(inspect.getfullargspec(aliases).args) == 1:
+                func.__mb_is_command_match__ = lambda self, val: aliases(val)
+            else:
+                func.__mb_is_command_match__ = aliases
+        elif isinstance(aliases, (list, set, tuple)):
+            func.__mb_is_command_match__ = lambda self, val: (val == func.__mb_name__
+                                                              or val in aliases)
+        else:
+            func.__mb_is_command_match__ = lambda self, val: val == func.__mb_name__
+        # Decorators are executed last to first, so we reverse the argument list.
+        func.__mb_arguments__.reverse()
+        func.__mb_require_subcommand__ = require_subcommand
+        func.__mb_arg_fallthrough__ = arg_fallthrough
+        func.__mb_event_type__ = event_type
+        return func
+
+    return decorator
+
+
+class ArgumentSyntaxError(ValueError):
+    def __init__(self, message: str, show_usage: bool = True) -> None:
+        super().__init__(message)
+        self.message = message
+        self.show_usage = show_usage
+
+
+class Argument(ABC):
+    def __init__(self, name: str, label: str = None, *, required: bool = False,
+                 pass_raw: bool = False) -> None:
+        self.name = name
+        self.label = label or name
+        self.required = required
+        self.pass_raw = pass_raw
+
+    @abstractmethod
+    def match(self, val: str) -> Tuple[str, Any]:
+        pass
+
+    def __call__(self, func: Union[CommandHandler, CommandHandlerFunc]) -> CommandHandler:
+        if not isinstance(func, CommandHandler):
+            func = CommandHandler(func)
+        func.__mb_arguments__.append(self)
+        return func
+
+
+class RegexArgument(Argument):
+    def __init__(self, name: str, label: str = None, *, required: bool = False,
+                 pass_raw: bool = False, matches: str = None) -> None:
+        super().__init__(name, label, required=required, pass_raw=pass_raw)
+        matches = f"^{matches}" if self.pass_raw else f"^{matches}$"
+        self.regex = re.compile(matches)
+
+    def match(self, val: str) -> Tuple[str, Any]:
+        orig_val = val
+        if not self.pass_raw:
+            val = val.split(" ")[0]
+        match = self.regex.match(val)
+        if match:
+            return (orig_val[:match.pos] + orig_val[match.endpos:],
+                    match.groups() or val[match.pos:match.endpos])
+        return orig_val, None
+
+
+class CustomArgument(Argument):
+    def __init__(self, name: str, label: str = None, *, required: bool = False,
+                 pass_raw: bool = False, matcher: Callable[[str], Any]) -> None:
+        super().__init__(name, label, required=required, pass_raw=pass_raw)
+        self.matcher = matcher
+
+    def match(self, val: str) -> Tuple[str, Any]:
+        if self.pass_raw:
+            return self.matcher(val)
+        orig_val = val
+        val = val.split(" ")[0]
+        res = self.matcher(val)
+        if res:
+            return orig_val[len(val):], res
+        return orig_val, None
+
+
+class SimpleArgument(Argument):
+    def match(self, val: str) -> Tuple[str, Any]:
+        if self.pass_raw:
+            return "", val
+        res = val.split(" ")[0]
+        return val[len(res):], res
+
+
+def argument(name: str, label: str = None, *, required: bool = True, matches: Optional[str] = None,
+             parser: Optional[Callable[[str], Any]] = None, pass_raw: bool = False
+             ) -> CommandHandlerDecorator:
+    if matches:
+        return RegexArgument(name, label, required=required, matches=matches, pass_raw=pass_raw)
+    elif parser:
+        return CustomArgument(name, label, required=required, matcher=parser, pass_raw=pass_raw)
+    else:
+        return SimpleArgument(name, label, required=required, pass_raw=pass_raw)
+
+
+def passive(regex: Union[str, Pattern], *, msgtypes: Sequence[MessageType] = (MessageType.TEXT,),
+            field: Callable[[MaubotMessageEvent], str] = lambda evt: evt.content.body,
+            event_type: EventType = EventType.ROOM_MESSAGE, multiple: bool = False
+            ) -> PassiveCommandHandlerDecorator:
+    if not isinstance(regex, Pattern):
+        regex = re.compile(regex)
+
+    def decorator(func: CommandHandlerFunc) -> CommandHandlerFunc:
+        combine = None
+        if hasattr(func, "__mb_passive_orig__"):
+            combine = func
+            func = func.__mb_passive_orig__
+
+        @event.on(event_type)
+        @functools.wraps(func)
+        async def replacement(self, evt: MaubotMessageEvent = None) -> None:
+            if not evt and isinstance(self, MaubotMessageEvent):
+                evt = self
+                self = None
+            if evt.sender == evt.client.mxid:
+                return
+            elif msgtypes and evt.content.msgtype not in msgtypes:
+                return
+            data = field(evt)
+            if multiple:
+                val = [(data[match.pos:match.endpos], *match.groups())
+                       for match in regex.finditer(data)]
+            else:
+                match = regex.match(data)
+                if match:
+                    val = (data[match.pos:match.endpos], *match.groups())
+                else:
+                    val = None
+            if val:
+                if self:
+                    await func(self, evt, val)
+                else:
+                    await func(evt, val)
+
+        if combine:
+            orig_replacement = replacement
+
+            @event.on(event_type)
+            @functools.wraps(func)
+            async def replacement(self, evt: MaubotMessageEvent = None) -> None:
+                await asyncio.gather(combine(self, evt), orig_replacement(self, evt))
+
+        replacement.__mb_passive_orig__ = func
+
+        return replacement
+
+    return decorator
diff --git a/maubot/handlers/event.py b/maubot/handlers/event.py
new file mode 100644
index 0000000..d6bde8e
--- /dev/null
+++ b/maubot/handlers/event.py
@@ -0,0 +1,34 @@
+# maubot - A plugin-based Matrix bot system.
+# Copyright (C) 2018 Tulir Asokan
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from typing import Callable, Union, NewType
+
+from mautrix.types import EventType
+from mautrix.client import EventHandler
+
+EventHandlerDecorator = NewType("EventHandlerDecorator", Callable[[EventHandler], EventHandler])
+
+
+def on(var: Union[EventType, EventHandler]) -> Union[EventHandlerDecorator, EventHandler]:
+    def decorator(func: EventHandler) -> EventHandler:
+        func.__mb_event_handler__ = True
+        if isinstance(var, EventType):
+            func.__mb_event_type__ = var
+        else:
+            func.__mb_event_type__ = EventType.ALL
+
+        return func
+
+    return decorator if isinstance(var, EventType) else decorator(var)
diff --git a/maubot/instance.py b/maubot/instance.py
index 3809c5c..15ef6ba 100644
--- a/maubot/instance.py
+++ b/maubot/instance.py
@@ -15,12 +15,14 @@
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 from typing import Dict, List, Optional
 from asyncio import AbstractEventLoop
+import os.path
 import logging
 import io
 
-from sqlalchemy.orm import Session
 from ruamel.yaml.comments import CommentedMap
 from ruamel.yaml import YAML
+from sqlalchemy.orm import Session
+import sqlalchemy as sql
 
 from mautrix.util.config import BaseProxyConfig, RecursiveDict
 from mautrix.types import UserID
@@ -133,8 +135,12 @@ class PluginInstance:
             except (FileNotFoundError, KeyError):
                 self.base_cfg = None
             self.config = config_class(self.load_config, lambda: self.base_cfg, self.save_config)
-        self.plugin = cls(self.client.client, self.loop, self.client.http_client, self.id,
-                          self.log, self.config, self.mb_config["plugin_directories.db"])
+        db = None
+        if self.loader.meta.database:
+            db_path = os.path.join(self.mb_config["plugin_directories.db"], self.id)
+            db = sql.create_engine(f"sqlite:///{db_path}.db")
+        self.plugin = cls(client=self.client.client, loop=self.loop, http=self.client.http_client,
+                          instance_id=self.id, log=self.log, config=self.config, database=db)
         try:
             await self.plugin.start()
         except Exception:
diff --git a/maubot/loader/abc.py b/maubot/loader/abc.py
index 24bd622..f4b62a7 100644
--- a/maubot/loader/abc.py
+++ b/maubot/loader/abc.py
@@ -22,6 +22,7 @@ from packaging.version import Version, InvalidVersion
 from mautrix.client.api.types.util import (SerializableAttrs, SerializerError, serializer,
                                            deserializer)
 
+from ..__meta__ import __version__
 from ..plugin_base import Plugin
 
 if TYPE_CHECKING:
@@ -51,9 +52,12 @@ def deserialize_version(version: str) -> Version:
 class PluginMeta(SerializableAttrs['PluginMeta']):
     id: str
     version: Version
-    license: str
     modules: List[str]
     main_class: str
+
+    maubot: Version = Version(__version__)
+    database: bool = False
+    license: str = ""
     extra_files: List[str] = []
     dependencies: List[str] = []
     soft_dependencies: List[str] = []
diff --git a/maubot/matrix.py b/maubot/matrix.py
index c152af9..1cb2d6e 100644
--- a/maubot/matrix.py
+++ b/maubot/matrix.py
@@ -13,18 +13,15 @@
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
-from typing import Dict, List, Union, Callable, Awaitable, Optional, Tuple
+from typing import Union, Awaitable, Optional, Tuple
 from markdown.extensions import Extension
 import markdown as md
 import attr
 
 from mautrix import Client as MatrixClient
 from mautrix.util.formatter import parse_html
-from mautrix.client import EventHandler
 from mautrix.types import (EventType, MessageEvent, Event, EventID, RoomID, MessageEventContent,
-                           MessageType, TextMessageEventContent, Format, RelatesTo)
-
-from .command_spec import ParsedCommand, CommandSpec
+                           MessageType, TextMessageEventContent, Format, RelatesTo, StateEvent)
 
 
 class EscapeHTML(Extension):
@@ -42,12 +39,12 @@ def parse_markdown(markdown: str, allow_html: bool = False) -> Tuple[str, str]:
 
 
 class MaubotMessageEvent(MessageEvent):
-    _client: MatrixClient
+    client: MatrixClient
 
     def __init__(self, base: MessageEvent, client: MatrixClient):
         super().__init__(**{a.name.lstrip("_"): getattr(base, a.name)
                             for a in attr.fields(MessageEvent)})
-        self._client = client
+        self.client = client
 
     def respond(self, content: Union[str, MessageEventContent],
                 event_type: EventType = EventType.ROOM_MESSAGE,
@@ -59,7 +56,7 @@ class MaubotMessageEvent(MessageEvent):
                 content.body, content.formatted_body = parse_markdown(content.body)
         if reply:
             content.set_reply(self)
-        return self._client.send_message_event(self.room_id, event_type, content)
+        return self.client.send_message_event(self.room_id, event_type, content)
 
     def reply(self, content: Union[str, MessageEventContent],
               event_type: EventType = EventType.ROOM_MESSAGE,
@@ -67,18 +64,10 @@ class MaubotMessageEvent(MessageEvent):
         return self.respond(content, event_type, markdown, reply=True)
 
     def mark_read(self) -> Awaitable[None]:
-        return self._client.send_receipt(self.room_id, self.event_id, "m.read")
+        return self.client.send_receipt(self.room_id, self.event_id, "m.read")
 
 
 class MaubotMatrixClient(MatrixClient):
-    def __init__(self, *args, **kwargs):
-        super().__init__(*args, **kwargs)
-        self.command_handlers: Dict[str, List[EventHandler]] = {}
-        self.commands: List[ParsedCommand] = []
-        self.command_specs: Dict[str, CommandSpec] = {}
-
-        self.add_event_handler(self._command_event_handler, EventType.ROOM_MESSAGE)
-
     def send_markdown(self, room_id: RoomID, markdown: str, msgtype: MessageType = MessageType.TEXT,
                       relates_to: Optional[RelatesTo] = None, **kwargs) -> Awaitable[EventID]:
         content = TextMessageEventContent(msgtype=msgtype, format=Format.HTML)
@@ -87,60 +76,17 @@ class MaubotMatrixClient(MatrixClient):
             content.relates_to = relates_to
         return self.send_message(room_id, content, **kwargs)
 
-    def set_command_spec(self, plugin_id: str, spec: CommandSpec) -> None:
-        self.command_specs[plugin_id] = spec
-        self._reparse_command_specs()
-
-    def _reparse_command_specs(self) -> None:
-        self.commands = [parsed_command
-                         for spec in self.command_specs.values()
-                         for parsed_command in spec.parse()]
-
-    def remove_command_spec(self, plugin_id: str) -> None:
-        try:
-            del self.command_specs[plugin_id]
-            self._reparse_command_specs()
-        except KeyError:
-            pass
-
-    async def _command_event_handler(self, evt: MessageEvent) -> None:
-        if evt.sender == self.mxid or evt.content.msgtype == MessageType.NOTICE:
-            return
-        for command in self.commands:
-            if command.match(evt):
-                await self._trigger_command(command, evt)
-                return
-
-    async def _trigger_command(self, command: ParsedCommand, evt: MessageEvent) -> None:
-        for handler in self.command_handlers.get(command.name, []):
-            await handler(evt)
-
-    def on(self, var: Union[EventHandler, EventType, str]
-           ) -> Union[EventHandler, Callable[[EventHandler], EventHandler]]:
-        if isinstance(var, str):
-            def decorator(func: EventHandler) -> EventHandler:
-                self.add_command_handler(var, func)
-                return func
-
-            return decorator
-        return super().on(var)
-
-    def add_command_handler(self, command: str, handler: EventHandler) -> None:
-        self.command_handlers.setdefault(command, []).append(handler)
-
-    def remove_command_handler(self, command: str, handler: EventHandler) -> None:
-        try:
-            self.command_handlers[command].remove(handler)
-        except (KeyError, ValueError):
-            pass
-
     async def call_handlers(self, event: Event) -> None:
         if isinstance(event, MessageEvent):
             event = MaubotMessageEvent(event, self)
+        else:
+            event.client = self
         return await super().call_handlers(event)
 
     async def get_event(self, room_id: RoomID, event_id: EventID) -> Event:
         event = await super().get_event(room_id, event_id)
         if isinstance(event, MessageEvent):
             return MaubotMessageEvent(event, self)
+        else:
+            event.client = self
         return event
diff --git a/maubot/plugin_base.py b/maubot/plugin_base.py
index 3925513..c720cc5 100644
--- a/maubot/plugin_base.py
+++ b/maubot/plugin_base.py
@@ -14,21 +14,18 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 from typing import Type, Optional, TYPE_CHECKING
+from abc import ABC
 from logging import Logger
-from abc import ABC, abstractmethod
 from asyncio import AbstractEventLoop
-from aiohttp import ClientSession
-import os.path
+import functools
 
 from sqlalchemy.engine.base import Engine
-import sqlalchemy as sql
+from aiohttp import ClientSession
 
 if TYPE_CHECKING:
-    from .client import MaubotMatrixClient
-    from .command_spec import CommandSpec
+    from mautrix.types import Event
     from mautrix.util.config import BaseProxyConfig
-
-DatabaseNotConfigured = ValueError("A database for this maubot instance has not been configured.")
+    from .client import MaubotMatrixClient
 
 
 class Plugin(ABC):
@@ -37,33 +34,30 @@ class Plugin(ABC):
     log: Logger
     loop: AbstractEventLoop
     config: Optional['BaseProxyConfig']
+    database: Optional[Engine]
 
     def __init__(self, client: 'MaubotMatrixClient', loop: AbstractEventLoop, http: ClientSession,
-                 plugin_instance_id: str, log: Logger, config: Optional['BaseProxyConfig'],
-                 db_base_path: str) -> None:
+                 instance_id: str, log: Logger, config: Optional['BaseProxyConfig'],
+                 database: Optional[Engine]) -> None:
         self.client = client
         self.loop = loop
         self.http = http
-        self.id = plugin_instance_id
+        self.id = instance_id
         self.log = log
         self.config = config
-        self.__db_base_path = db_base_path
+        self.database = database
+        self._handlers_at_startup = []
 
-    def request_db_engine(self) -> Optional[Engine]:
-        if not self.__db_base_path:
-            raise DatabaseNotConfigured
-        return sql.create_engine(f"sqlite:///{os.path.join(self.__db_base_path, self.id)}.db")
-
-    def set_command_spec(self, spec: 'CommandSpec') -> None:
-        self.client.set_command_spec(self.id, spec)
-
-    @abstractmethod
     async def start(self) -> None:
-        pass
+        for key in dir(self):
+            val = getattr(self, key)
+            if hasattr(val, "__mb_event_handler__") and val.__mb_event_handler__:
+                self._handlers_at_startup.append((val, val.__mb_event_type__))
+                self.client.add_event_handler(val.__mb_event_type__, val)
 
-    @abstractmethod
     async def stop(self) -> None:
-        pass
+        for func, event_type in self._handlers_at_startup:
+            self.client.remove_event_handler(event_type, func)
 
     @classmethod
     def get_config_class(cls) -> Optional[Type['BaseProxyConfig']]: