diff --git a/inbox/api/kellogs.py b/inbox/api/kellogs.py
index f3acd3965..a6e061797 100644
--- a/inbox/api/kellogs.py
+++ b/inbox/api/kellogs.py
@@ -1,6 +1,7 @@
 import calendar
 import datetime
 from json import JSONEncoder, dumps
+from typing import Any, TypedDict, overload
 
 import arrow  # type: ignore[import-untyped]
 from flask import Response
@@ -15,8 +16,10 @@
     Contact,
     Event,
     Message,
+    MessageCategory,
     Metadata,
     Namespace,
+    PhoneNumber,
     Thread,
     When,
 )
@@ -30,13 +33,28 @@
 log = get_logger()
 
 
-def format_address_list(addresses):  # type: ignore[no-untyped-def]  # noqa: ANN201
+class FormattedAddress(TypedDict):
+    name: str
+    email: str
+
+
+def format_address_list(
+    addresses: list[tuple[str, str]] | None
+) -> list[FormattedAddress]:
     if addresses is None:
         return []
     return [{"name": name, "email": email} for name, email in addresses]
 
 
-def format_categories(categories):  # type: ignore[no-untyped-def]  # noqa: ANN201
+class FormattedCategory(TypedDict):
+    id: str
+    name: str | None
+    display_name: str
+
+
+def format_categories(
+    categories: set[Category] | None,
+) -> list[FormattedCategory]:
     if categories is None:
         return []
     return [
@@ -46,13 +64,20 @@ def format_categories(categories):  # type: ignore[no-untyped-def]  # noqa: ANN2
             "display_name": category.api_display_name,
         }
         for category in categories
-        if category
+        if category  # type: ignore[truthy-bool]
     ]
 
 
-def format_messagecategories(  # type: ignore[no-untyped-def]  # noqa: ANN201
-    messagecategories,
-):
+class FormattedMessageCategory(TypedDict):
+    id: str
+    name: str | None
+    display_name: str
+    created_timestamp: datetime.datetime
+
+
+def format_messagecategories(
+    messagecategories: list[MessageCategory] | None,
+) -> list[FormattedMessageCategory]:
     if messagecategories is None:
         return []
     return [
@@ -67,18 +92,55 @@ def format_messagecategories(  # type: ignore[no-untyped-def]  # noqa: ANN201
     ]
 
 
-def format_phone_numbers(phone_numbers):  # type: ignore[no-untyped-def]  # noqa: ANN201
-    formatted_phone_numbers = []
-    for number in phone_numbers:
-        formatted_phone_numbers.append(
-            {"type": number.type, "number": number.number}
-        )
-    return formatted_phone_numbers
+class FormattedPhoneNumber(TypedDict):
+    type: str
+    number: str
+
 
+def format_phone_numbers(
+    phone_numbers: list[PhoneNumber],
+) -> list[FormattedPhoneNumber]:
+    return [
+        {"type": number.type, "number": number.number}
+        for number in phone_numbers
+    ]
 
-def encode(  # type: ignore[no-untyped-def]  # noqa: ANN201
-    obj, namespace_public_id=None, expand: bool = False, is_n1: bool = False
-):
+
+@overload
+def encode(
+    obj: datetime.date,
+    namespace_public_id: str | None = None,
+    expand: bool = False,
+    is_n1: bool = False,
+) -> str | int: ...
+
+
+@overload
+def encode(
+    obj: (
+        Namespace
+        | Message
+        | Thread
+        | Contact
+        | Event
+        | Calendar
+        | When
+        | Block
+        | Category
+        | Metadata
+    ),
+    namespace_public_id: str | None = None,
+    expand: bool = False,
+    is_n1: bool = False,
+) -> dict[str, Any]: ...
+
+
+def encode(
+    obj: Any,
+    namespace_public_id: str | None = None,
+    expand: bool = False,
+    is_n1: bool = False,
+) -> dict[str, Any] | str | int | None:
     try:
         return _encode(obj, namespace_public_id, expand, is_n1=is_n1)
     except Exception as e:
@@ -93,7 +155,7 @@ def encode(  # type: ignore[no-untyped-def]  # noqa: ANN201
         raise
 
 
-def _convert_timezone_to_iana_tz(original_tz):  # type: ignore[no-untyped-def]
+def _convert_timezone_to_iana_tz(original_tz: str | None) -> str | None:
     if original_tz is None:
         return None
 
@@ -104,9 +166,41 @@ def _convert_timezone_to_iana_tz(original_tz):  # type: ignore[no-untyped-def]
         return original_tz
 
 
-def _encode(  # type: ignore[no-untyped-def]  # noqa: D417
-    obj, namespace_public_id=None, expand: bool = False, is_n1: bool = False
-):
+@overload
+def _encode(
+    obj: datetime.date,
+    namespace_public_id: str | None = None,
+    expand: bool = False,
+    is_n1: bool = False,
+) -> str | int: ...
+
+
+@overload
+def _encode(
+    obj: (
+        Namespace
+        | Message
+        | Thread
+        | Contact
+        | Event
+        | Calendar
+        | When
+        | Block
+        | Category
+        | Metadata
+    ),
+    namespace_public_id: str | None = None,
+    expand: bool = False,
+    is_n1: bool = False,
+) -> dict[str, Any]: ...
+
+
+def _encode(  # noqa: D417
+    obj: Any,
+    namespace_public_id: str | None = None,
+    expand: bool = False,
+    is_n1: bool = False,
+) -> dict[str, Any] | int | str | None:
     """
     Returns a dictionary representation of a Nylas model object obj, or
     None if there is no such representation defined. If the optional
@@ -126,10 +220,12 @@ def _encode(  # type: ignore[no-untyped-def]  # noqa: D417
 
     """  # noqa: D401
 
-    def _get_namespace_public_id(obj):  # type: ignore[no-untyped-def]
+    def _get_namespace_public_id(obj: Any) -> str | None:
         return namespace_public_id or obj.namespace.public_id
 
-    def _format_participant_data(participant):  # type: ignore[no-untyped-def]
+    def _format_participant_data(
+        participant: dict[str, Any]
+    ) -> dict[str, Any]:
         """
         Event.participants is a JSON blob which may contain internal data.
         This function returns a dict with only the data we want to make
@@ -141,7 +237,7 @@ def _format_participant_data(participant):  # type: ignore[no-untyped-def]
 
         return dct
 
-    def _get_lowercase_class_name(obj):  # type: ignore[no-untyped-def]
+    def _get_lowercase_class_name(obj: Any) -> str:
         return type(obj).__name__.lower()
 
     # Flask's jsonify() doesn't handle datetimes or json arrays as primary
@@ -211,13 +307,15 @@ def _get_lowercase_class_name(obj):  # type: ignore[no-untyped-def]
             ],
         }
 
-        categories = format_messagecategories(
+        message_categories = format_messagecategories(
             obj.messagecategories  # type: ignore[attr-defined]
         )
         if obj.namespace.account.category_type == "folder":
-            resp["folder"] = categories[0] if categories else None
+            resp["folder"] = (
+                message_categories[0] if message_categories else None
+            )
         else:
-            resp["labels"] = categories
+            resp["labels"] = message_categories
 
         # If the message is a draft (Nylas-created or otherwise):
         if obj.is_draft:
@@ -296,11 +394,15 @@ def _get_lowercase_class_name(obj):  # type: ignore[no-untyped-def]
                     "References": msg.references,
                 },
             }
-            categories = format_messagecategories(msg.messagecategories)
+            message_categories = format_messagecategories(
+                msg.messagecategories
+            )
             if obj.namespace.account.category_type == "folder":
-                resp["folder"] = categories[0] if categories else None
+                resp["folder"] = (
+                    message_categories[0] if message_categories else None
+                )
             else:
-                resp["labels"] = categories
+                resp["labels"] = message_categories
 
             if msg.is_draft:
                 resp["object"] = "draft"
@@ -473,9 +575,9 @@ class APIEncoder:
 
     """
 
-    def __init__(  # type: ignore[no-untyped-def]
+    def __init__(
         self,
-        namespace_public_id=None,
+        namespace_public_id: str | None = None,
         expand: bool = False,
         is_n1: bool = False,
     ) -> None:
@@ -483,11 +585,14 @@ def __init__(  # type: ignore[no-untyped-def]
             namespace_public_id, expand, is_n1=is_n1
         )
 
-    def _encoder_factory(  # type: ignore[no-untyped-def]
-        self, namespace_public_id, expand, is_n1: bool = False
-    ):
+    def _encoder_factory(
+        self,
+        namespace_public_id: str | None,
+        expand: bool,
+        is_n1: bool = False,
+    ) -> type[JSONEncoder]:
         class InternalEncoder(JSONEncoder):
-            def default(self, obj):  # type: ignore[no-untyped-def]
+            def default(self, obj: Any) -> Any:
                 custom_representation = encode(
                     obj, namespace_public_id, expand=expand, is_n1=is_n1
                 )
@@ -498,9 +603,7 @@ def default(self, obj):  # type: ignore[no-untyped-def]
 
         return InternalEncoder
 
-    def cereal(  # type: ignore[no-untyped-def]  # noqa: ANN201, D417
-        self, obj, pretty: bool = False
-    ):
+    def cereal(self, obj: Any, pretty: bool = False) -> str:  # noqa: D417
         """
         Returns the JSON string representation of obj.
 
@@ -526,7 +629,7 @@ def cereal(  # type: ignore[no-untyped-def]  # noqa: ANN201, D417
             )
         return dumps(obj, cls=self.encoder_class)
 
-    def jsonify(self, obj):  # type: ignore[no-untyped-def]  # noqa: ANN201, D417
+    def jsonify(self, obj: Any) -> Response:  # noqa: D417
         """
         Returns a Flask Response object encapsulating the JSON
         representation of obj.
diff --git a/inbox/api/sending.py b/inbox/api/sending.py
index ac15645ca..0776dec84 100644
--- a/inbox/api/sending.py
+++ b/inbox/api/sending.py
@@ -3,6 +3,7 @@
 from inbox.api.err import err
 from inbox.api.kellogs import APIEncoder, encode
 from inbox.logging import get_logger
+from inbox.models import Message
 from inbox.sendmail.base import SendMailException, get_sendmail_client
 
 log = get_logger()
@@ -31,7 +32,7 @@ def send_draft(account, draft, db_session):  # type: ignore[no-untyped-def]  # n
 
 
 def send_draft_copy(  # type: ignore[no-untyped-def]  # noqa: ANN201
-    account, draft, custom_body, recipient
+    account, draft: Message, custom_body, recipient
 ):
     """
     Sends a copy of this draft to the recipient, using the specified body
@@ -39,14 +40,14 @@ def send_draft_copy(  # type: ignore[no-untyped-def]  # noqa: ANN201
     sent. Used within multi-send to send messages to individual recipients
     with customized bodies.
     """  # noqa: D401
-    # Create the response to send on success by serlializing the draft. After
+    # Create the response to send on success by serializing the draft. After
     # serializing, we replace the new custom body (which the recipient will get
     # and which should be returned in this response) in place of the existing
     # body (which we still need to retain in the draft for when it's saved to
     # the sent folder).
     response_on_success = encode(draft)
     response_on_success["body"] = custom_body
-    response_on_success = APIEncoder().jsonify(response_on_success)
+    encoded_response = APIEncoder().jsonify(response_on_success)
 
     # Now send the draft to the specified recipient. The send_custom method
     # will write the custom body into the message in place of the one in the
@@ -62,7 +63,7 @@ def send_draft_copy(  # type: ignore[no-untyped-def]  # noqa: ANN201
             kwargs["server_error"] = exc.server_error
         return err(exc.http_code, exc.args[0], **kwargs)
 
-    return response_on_success
+    return encoded_response
 
 
 def update_draft_on_send(  # type: ignore[no-untyped-def]
diff --git a/inbox/api/validation.py b/inbox/api/validation.py
index f91fb5327..2c8cc494e 100644
--- a/inbox/api/validation.py
+++ b/inbox/api/validation.py
@@ -1,7 +1,7 @@
 """Utilities for validating user input to the API."""
 
 import contextlib
-from typing import Never
+from typing import Any, Never
 
 import arrow  # type: ignore[import-untyped]
 from arrow.parser import ParserError  # type: ignore[import-untyped]
@@ -161,9 +161,9 @@ def strict_parse_args(parser, raw_args):  # type: ignore[no-untyped-def]  # noqa
     return args
 
 
-def get_sending_draft(  # type: ignore[no-untyped-def]  # noqa: ANN201
+def get_sending_draft(  # type: ignore[no-untyped-def]
     draft_public_id, namespace_id, db_session
-):
+) -> Message:
     valid_public_id(draft_public_id)
     try:
         draft = (
@@ -398,7 +398,7 @@ def valid_event_update(  # type: ignore[no-untyped-def]
             )
 
 
-def noop_event_update(event, data) -> bool:  # type: ignore[no-untyped-def]
+def noop_event_update(event: Event, data: dict[str, Any]) -> bool:
     # Check whether the update is actually updating fields.
     # We do this by cloning the event, updating the fields and
     # comparing them. This is less cumbersome than having to think
@@ -469,7 +469,7 @@ def valid_delta_object_types(types_arg):  # type: ignore[no-untyped-def]  # noqa
     return types
 
 
-def validate_draft_recipients(draft) -> None:  # type: ignore[no-untyped-def]
+def validate_draft_recipients(draft: Message) -> None:
     """
     Check that a draft has at least one recipient, and that all recipient
     emails are at least plausible email addresses, before we try to send it.