diff --git a/tools/run-mypy b/tools/run-mypy
index c5f9e3c16..7106f90f7 100755
--- a/tools/run-mypy
+++ b/tools/run-mypy
@@ -22,7 +22,6 @@ exclude = [
     "zulip_bots/zulip_bots/bots",
     "zulip_bots/zulip_bots/bots_unmaintained",
     # Excluded out of laziness:
-    "zulip_bots/zulip_bots/simple_lib.py",
     "zulip_bots/zulip_bots/tests/test_lib.py",
 ]
 
diff --git a/zulip_bots/zulip_bots/simple_lib.py b/zulip_bots/zulip_bots/simple_lib.py
index 24c2c7606..ed82f2b83 100644
--- a/zulip_bots/zulip_bots/simple_lib.py
+++ b/zulip_bots/zulip_bots/simple_lib.py
@@ -1,61 +1,62 @@
 import configparser
 import sys
+from typing import IO, Any, Dict, Optional
 from uuid import uuid4
 
 from zulip_bots.lib import BotIdentity
 
 
 class SimpleStorage:
-    def __init__(self):
-        self.data = dict()
+    def __init__(self) -> None:
+        self.data: Dict[str, Any] = dict()
 
-    def contains(self, key):
+    def contains(self, key: str) -> bool:
         return key in self.data
 
-    def put(self, key, value):
+    def put(self, key: str, value: Any) -> None:
         self.data[key] = value
 
-    def get(self, key):
+    def get(self, key: str) -> Any:
         return self.data[key]
 
 
 class MockMessageServer:
     # This class is needed for the incrementor bot, which
     # actually updates messages!
-    def __init__(self):
+    def __init__(self) -> None:
         self.message_id = 0
-        self.messages = dict()
+        self.messages: Dict[int, Dict[str, Any]] = dict()
 
-    def send(self, message):
+    def send(self, message: Dict[str, Any]) -> Dict[str, Any]:
         self.message_id += 1
         message["id"] = self.message_id
         self.messages[self.message_id] = message
         return message
 
-    def add_reaction(self, reaction_data):
+    def add_reaction(self, reaction_data: object) -> Dict[str, Any]:
         return dict(result="success", msg="", uri=f"https://server/messages/{uuid4()}/reactions")
 
-    def update(self, message):
+    def update(self, message: Dict[str, Any]) -> None:
         self.messages[message["message_id"]] = message
 
-    def upload_file(self, file):
+    def upload_file(self, file: IO[Any]) -> Dict[str, Any]:
         return dict(result="success", msg="", uri=f"https://server/user_uploads/{uuid4()}")
 
 
 class TerminalBotHandler:
-    def __init__(self, bot_config_file, message_server):
+    def __init__(self, bot_config_file: Optional[str], message_server: MockMessageServer) -> None:
         self.bot_config_file = bot_config_file
         self._storage = SimpleStorage()
         self.message_server = message_server
 
     @property
-    def storage(self):
+    def storage(self) -> SimpleStorage:
         return self._storage
 
-    def identity(self):
+    def identity(self) -> BotIdentity:
         return BotIdentity("bot name", "bot-email@domain")
 
-    def react(self, message, emoji_name):
+    def react(self, message: Dict[str, Any], emoji_name: str) -> Dict[str, Any]:
         """
         Mock adding an emoji reaction and print it in the terminal.
         """
@@ -64,7 +65,7 @@ def react(self, message, emoji_name):
             dict(message_id=message["id"], emoji_name=emoji_name, reaction_type="unicode_emoji")
         )
 
-    def send_message(self, message):
+    def send_message(self, message: Dict[str, Any]) -> Dict[str, Any]:
         """
         Print the message sent in the terminal and store it in a mock message server.
         """
@@ -90,7 +91,7 @@ def send_message(self, message):
         # id to the message instead of actually displaying it.
         return self.message_server.send(message)
 
-    def send_reply(self, message, response):
+    def send_reply(self, message: Dict[str, Any], response: str) -> Dict[str, Any]:
         """
         Print the reply message in the terminal and store it in a mock message server.
         """
@@ -102,7 +103,7 @@ def send_reply(self, message, response):
         response_message = dict(content=response)
         return self.message_server.send(response_message)
 
-    def update_message(self, message):
+    def update_message(self, message: Dict[str, Any]) -> None:
         """
         Update a previously sent message and print the result in the terminal.
         Throw an IndexError if the message id is invalid.
@@ -117,14 +118,14 @@ def update_message(self, message):
             )
         )
 
-    def upload_file_from_path(self, file_path):
+    def upload_file_from_path(self, file_path: str) -> Dict[str, Any]:
         with open(file_path) as file:
             return self.upload_file(file)
 
-    def upload_file(self, file):
+    def upload_file(self, file: IO[Any]) -> Dict[str, Any]:
         return self.message_server.upload_file(file)
 
-    def get_config_info(self, bot_name, optional=False):
+    def get_config_info(self, bot_name: str, optional: bool = False) -> Dict[str, Any]:
         if self.bot_config_file is None:
             if optional:
                 return dict()