diff --git a/keyserver/src/responders/activity-responders.js b/keyserver/src/responders/activity-responders.js
--- a/keyserver/src/responders/activity-responders.js
+++ b/keyserver/src/responders/activity-responders.js
@@ -1,13 +1,14 @@
 // @flow
 
 import t from 'tcomb';
-import type { TList, TInterface } from 'tcomb';
+import type { TList } from 'tcomb';
 
 import type {
   UpdateActivityResult,
   UpdateActivityRequest,
   SetThreadUnreadStatusRequest,
   SetThreadUnreadStatusResult,
+  ActivityUpdate,
 } from 'lib/types/activity-types.js';
 import { tShape } from 'lib/utils/validation-utils.js';
 
@@ -18,7 +19,7 @@
 } from '../updaters/activity-updaters.js';
 import { validateInput } from '../utils/validation-utils.js';
 
-const activityUpdatesInputValidator: TList<TInterface> = t.list(
+const activityUpdatesInputValidator: TList<Array<ActivityUpdate>> = t.list(
   tShape({
     focus: t.Bool,
     threadID: t.String,
diff --git a/keyserver/src/responders/device-responders.js b/keyserver/src/responders/device-responders.js
--- a/keyserver/src/responders/device-responders.js
+++ b/keyserver/src/responders/device-responders.js
@@ -10,11 +10,12 @@
 import { deviceTokenUpdater } from '../updaters/device-token-updaters.js';
 import { validateInput } from '../utils/validation-utils.js';
 
-const deviceTokenUpdateRequestInputValidator: TInterface = tShape({
-  deviceToken: t.maybe(t.String),
-  deviceType: t.maybe(t.enums.of(['ios', 'android'])),
-  platformDetails: t.maybe(tPlatformDetails),
-});
+const deviceTokenUpdateRequestInputValidator: TInterface<DeviceTokenUpdateRequest> =
+  tShape({
+    deviceToken: t.maybe(t.String),
+    deviceType: t.maybe(t.enums.of(['ios', 'android'])),
+    platformDetails: t.maybe(tPlatformDetails),
+  });
 
 async function deviceTokenUpdateResponder(
   viewer: Viewer,
diff --git a/keyserver/src/responders/entry-responders.js b/keyserver/src/responders/entry-responders.js
--- a/keyserver/src/responders/entry-responders.js
+++ b/keyserver/src/responders/entry-responders.js
@@ -16,7 +16,10 @@
   DeltaEntryInfosResult,
   SaveEntryResponse,
 } from 'lib/types/entry-types.js';
-import { calendarThreadFilterTypes } from 'lib/types/filter-types.js';
+import {
+  type CalendarFilter,
+  calendarThreadFilterTypes,
+} from 'lib/types/filter-types.js';
 import type {
   FetchEntryRevisionInfosResult,
   FetchEntryRevisionInfosRequest,
@@ -40,7 +43,14 @@
 import { commitSessionUpdate } from '../updaters/session-updaters.js';
 import { validateInput } from '../utils/validation-utils.js';
 
-const entryQueryInputValidator: TInterface = tShape({
+type EntryQueryInput = {
+  +startDate: string,
+  +endDate: string,
+  +navID?: ?string,
+  +includeDeleted?: ?boolean,
+  +filters?: ?$ReadOnlyArray<CalendarFilter>,
+};
+const entryQueryInputValidator: TInterface<EntryQueryInput> = tShape({
   navID: t.maybe(t.String),
   startDate: tDate,
   endDate: tDate,
@@ -59,7 +69,8 @@
     ),
   ),
 });
-const newEntryQueryInputValidator: TInterface = tShape({
+
+const newEntryQueryInputValidator: TInterface<CalendarQuery> = tShape({
   startDate: tDate,
   endDate: tDate,
   filters: t.list(
diff --git a/keyserver/src/responders/report-responders.js b/keyserver/src/responders/report-responders.js
--- a/keyserver/src/responders/report-responders.js
+++ b/keyserver/src/responders/report-responders.js
@@ -9,6 +9,8 @@
   type ReportCreationRequest,
   type FetchErrorReportInfosResponse,
   type FetchErrorReportInfosRequest,
+  type ThreadInconsistencyReportShape,
+  type EntryInconsistencyReportShape,
   reportTypes,
 } from 'lib/types/report-types.js';
 import { ServerError } from 'lib/utils/errors.js';
@@ -32,27 +34,29 @@
   time: t.Number,
   summary: t.String,
 });
-const threadInconsistencyReportValidatorShape: TStructProps = {
-  platformDetails: tPlatformDetails,
-  beforeAction: t.Object,
-  action: t.Object,
-  pollResult: t.maybe(t.Object),
-  pushResult: t.Object,
-  lastActionTypes: t.maybe(t.list(t.String)),
-  lastActions: t.maybe(t.list(tActionSummary)),
-  time: t.maybe(t.Number),
-};
-const entryInconsistencyReportValidatorShape: TStructProps = {
-  platformDetails: tPlatformDetails,
-  beforeAction: t.Object,
-  action: t.Object,
-  calendarQuery: newEntryQueryInputValidator,
-  pollResult: t.maybe(t.Object),
-  pushResult: t.Object,
-  lastActionTypes: t.maybe(t.list(t.String)),
-  lastActions: t.maybe(t.list(tActionSummary)),
-  time: t.Number,
-};
+const threadInconsistencyReportValidatorShape: TStructProps<ThreadInconsistencyReportShape> =
+  {
+    platformDetails: tPlatformDetails,
+    beforeAction: t.Object,
+    action: t.Object,
+    pollResult: t.maybe(t.Object),
+    pushResult: t.Object,
+    lastActionTypes: t.maybe(t.list(t.String)),
+    lastActions: t.maybe(t.list(tActionSummary)),
+    time: t.maybe(t.Number),
+  };
+const entryInconsistencyReportValidatorShape: TStructProps<EntryInconsistencyReportShape> =
+  {
+    platformDetails: tPlatformDetails,
+    beforeAction: t.Object,
+    action: t.Object,
+    calendarQuery: newEntryQueryInputValidator,
+    pollResult: t.maybe(t.Object),
+    pushResult: t.Object,
+    lastActionTypes: t.maybe(t.list(t.String)),
+    lastActions: t.maybe(t.list(tActionSummary)),
+    time: t.Number,
+  };
 const userInconsistencyReportValidatorShape = {
   platformDetails: tPlatformDetails,
   action: t.Object,
diff --git a/keyserver/src/responders/thread-responders.js b/keyserver/src/responders/thread-responders.js
--- a/keyserver/src/responders/thread-responders.js
+++ b/keyserver/src/responders/thread-responders.js
@@ -1,7 +1,7 @@
 // @flow
 
 import t from 'tcomb';
-import type { TUnion, TInterface } from 'tcomb';
+import type { TUnion } from 'tcomb';
 
 import {
   type ThreadDeletionRequest,
@@ -138,7 +138,7 @@
   initialMemberIDs: t.maybe(t.list(t.String)),
   calendarQuery: t.maybe(entryQueryInputValidator),
 };
-const newThreadRequestInputValidator: TUnion<TInterface> = t.union([
+const newThreadRequestInputValidator: TUnion<ServerNewThreadRequest> = t.union([
   tShape({
     type: tNumEnum([threadTypes.SIDEBAR]),
     sourceMessageID: t.String,
diff --git a/keyserver/src/socket/session-utils.js b/keyserver/src/socket/session-utils.js
--- a/keyserver/src/socket/session-utils.js
+++ b/keyserver/src/socket/session-utils.js
@@ -2,7 +2,7 @@
 
 import invariant from 'invariant';
 import t from 'tcomb';
-import type { TUnion, TInterface } from 'tcomb';
+import type { TUnion } from 'tcomb';
 
 import {
   usersInRawEntryInfos,
@@ -74,7 +74,7 @@
 import type { SessionUpdate } from '../updaters/session-updaters.js';
 import { getOlmUtility } from '../utils/olm-utils.js';
 
-const clientResponseInputValidator: TUnion<TInterface> = t.union([
+const clientResponseInputValidator: TUnion<ClientResponse> = t.union([
   tShape({
     type: t.irreducible(
       'serverRequestTypes.PLATFORM',
diff --git a/lib/flow-typed/npm/tcomb_v3.x.x.js b/lib/flow-typed/npm/tcomb_v3.x.x.js
--- a/lib/flow-typed/npm/tcomb_v3.x.x.js
+++ b/lib/flow-typed/npm/tcomb_v3.x.x.js
@@ -2,532 +2,138 @@
 // flow-typed version: <<STUB>>/tcomb_v3.2.29/flow_v0.137.0
 
 declare module 'tcomb' {
-  declare type TBaseMeta = {
-    +kind: string,
-    +name: string,
-    +identity: boolean,
-    ...
-  };
-
-  declare export class TType<T, M = TBaseMeta> {
+  declare class TBaseType<+T> {
     (val: T): this;
     is(val: mixed): boolean;
     displayName: string;
-    meta: M;
-    t: T;
+    +t: T;
   }
 
-  declare export class TIrreducible<T> extends TType<T, {|
-    +kind: string,
-    +name: string,
-    +identity: boolean,
-    +predicate: mixed => boolean,
-  |}> { }
+  declare export type TType<+T> =
+    | TIrreducible<T>
+    | TMaybe<T>
+    | TList<T>
+    | TDict<T>
+    | TUnion<T>
+    | TEnums
+    | TRefinement<T>
+    | TInterface<T>;
+
+  declare export class TIrreducible<+T> extends TBaseType<T> {
+    meta: {
+      +kind: 'irreducible',
+      +name: string,
+      +identity: boolean,
+      +predicate: mixed => boolean,
+    };
+  }
+
+  declare export class TMaybe<+T> extends TBaseType<T> {
+    meta: {
+      +kind: 'maybe',
+      +name: string,
+      +identity: boolean,
+      +type: TType<T>,
+    };
+  }
 
-  declare export class TMaybe<T> extends TType<void | T, {|
-    +kind: string,
-    +name: string,
-    +identity: boolean,
-    +type: TType<T>,
-  |}> { }
+  declare export class TList<+T> extends TBaseType<T> {
+    meta: {
+      +kind: 'list',
+      +name: string,
+      +identity: boolean,
+      +type: TType<T>,
+    };
+  }
 
-  declare export class TList<T> extends TType<Array<T>, {|
-    +kind: string,
-    +name: string,
-    +identity: boolean,
-    +type: TType<T>,
-  |}> { }
+  declare export class TDict<+T> extends TBaseType<T> {
+    meta: {
+      +kind: 'dict',
+      +name: string,
+      +identity: boolean,
+      +domain: TType<string>,
+      +codomain: TType<T>,
+    };
+  }
 
-  declare export class TDict<T> extends TType<{ [key: string]: T }, {|
-    +kind: string,
-    +name: string,
-    +identity: boolean,
-    +domain: TType<string>,
-    +codomain: T,
-  |}> { }
+  declare export class TUnion<+T> extends TBaseType<T> {
+    meta: {
+      +kind: 'union',
+      +name: string,
+      +identity: boolean,
+      +types: Array<TType<T>>,
+    };
+  }
 
-  declare export class TUnion<T> extends TType<T, {|
-    +kind: string,
-    +name: string,
-    +identity: boolean,
-    +types: Array<TType<T>>,
-  |}> { }
+  declare export class TEnums extends TBaseType<string> {
+    meta: {
+      +kind: 'enums',
+      +name: string,
+      +identity: boolean,
+      +map: Object,
+    };
+  }
 
-  declare export class TEnums extends TType<string, {|
-    +kind: string,
-    +name: string,
-    +identity: boolean,
-    +map: Object,
-  |}> { }
+  declare export class TRefinement<+T> extends TBaseType<T> {
+    meta: {
+      +kind: 'subtype',
+      +name: string,
+      +identity: boolean,
+      +type: TType<T>,
+      +predicate: mixed => boolean,
+    };
+  }
 
-  declare export class TRefinement<T> extends TType<T, {|
-    +kind: string,
-    +name: string,
-    +identity: boolean,
-    +type: TType<T>,
-    +predicate: mixed => boolean,
-  |}> { }
+  declare type TypeToValidator = <V>(v: V) => TType<V>;
 
-  declare export type TStructProps = { [key: string]: TType<any, any> };
-  declare type TStructOptions = {|
+  declare export type TStructProps<+T> = $ObjMap<T, TypeToValidator>;
+  declare type TStructOptions = {
     name?: string,
     strict?: boolean,
     defaultProps?: Object,
-  |};
-  declare export class TInterface extends TType<any, {|
-    +kind: string,
-    +name: string,
-    +identity: boolean,
-    +props: TStructProps,
-    +strict: boolean,
-  |}> { }
+  };
+
+  declare export class TInterface<+T> extends TBaseType<T> {
+    meta: {
+      +kind: 'interface',
+      +name: string,
+      +identity: boolean,
+      +props: TStructProps<T>,
+      +strict: boolean,
+    };
+  }
 
   declare export default {
+    +Nil: TIrreducible<void | null>,
     +Bool: TIrreducible<boolean>,
     +Boolean: TIrreducible<boolean>,
     +String: TIrreducible<string>,
     +Number: TIrreducible<number>,
     +Object: TIrreducible<Object>,
-    maybe<T, M>(type: TType<T, M>, name?: string): TMaybe<T>,
-    list<T, M>(type: TType<T, M>, name?: string): TList<T>,
-    dict<T, M1, M2>(
-      domain: TType<string, M1>,
-      codomain: TType<T, M2>,
+    maybe<T>(type: TType<T>, name?: string): TMaybe<void | T>,
+    list<T>(type: TType<T>, name?: string): TList<Array<T>>,
+    dict<T>(
+      domain: TType<string>,
+      codomain: TType<T>,
       name?: string,
-    ): TDict<T>,
-    union<T, M>(types: Array<TType<T, M>>, name?: string): TUnion<T>,
-    +enums: {|
+    ): TDict<{ [key: string]: T }>,
+    union<+T>(types: $ReadOnlyArray<TType<T>>, name?: string): TUnion<T>,
+    +enums: {
       of(enums: $ReadOnlyArray<string>, name?: string): TEnums,
-    |},
-    irreducible<T>(name: string, predicate: mixed => boolean): TIrreducible<T>,
-    refinement<T, M>(
-      type: TType<T, M>,
-      predicate: T => boolean,
+    },
+    irreducible<T>(
+      name: string,
+      predicate: (mixed) => boolean,
+    ): TIrreducible<T>,
+    refinement<T>(
+      type: TType<T>,
+      predicate: (T) => boolean,
       name?: string,
     ): TRefinement<T>,
-    interface(
-      props: TStructProps,
+    interface<T>(
+      props: TStructProps<T>,
       options?: string | TStructOptions,
-    ): TInterface,
+    ): TInterface<T>,
     ...
   };
 }
-
-/**
- * We include stubs for each file inside this npm package in case you need to
- * require those files directly. Feel free to delete any files that aren't
- * needed.
- */
-declare module 'tcomb/lib/Any' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/Array' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/assert' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/assign' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/Boolean' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/create' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/Date' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/declare' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/decompose' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/dict' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/enums' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/Error' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/extend' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/fail' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/forbidNewOperator' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/fromJSON' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/func' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/Function' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/getDefaultInterfaceName' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/getFunctionName' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/getTypeName' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/installTypeFormatter' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/Integer' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/interface' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/intersection' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/irreducible' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/is' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isArray' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isBoolean' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isFunction' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isIdentity' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isInterface' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isMaybe' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isNil' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isNumber' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isObject' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isString' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isStruct' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isSubsetOf' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isType' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isTypeName' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/isUnion' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/list' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/match' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/maybe' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/mixin' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/Nil' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/Number' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/Object' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/refinement' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/RegExp' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/String' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/stringify' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/struct' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/tuple' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/Type' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/union' {
-  declare module.exports: any;
-}
-
-declare module 'tcomb/lib/update' {
-  declare module.exports: any;
-}
-
-// Filename aliases
-declare module 'tcomb/index' {
-  declare module.exports: $Exports<'tcomb'>;
-}
-declare module 'tcomb/index.js' {
-  declare module.exports: $Exports<'tcomb'>;
-}
-declare module 'tcomb/lib/Any.js' {
-  declare module.exports: $Exports<'tcomb/lib/Any'>;
-}
-declare module 'tcomb/lib/Array.js' {
-  declare module.exports: $Exports<'tcomb/lib/Array'>;
-}
-declare module 'tcomb/lib/assert.js' {
-  declare module.exports: $Exports<'tcomb/lib/assert'>;
-}
-declare module 'tcomb/lib/assign.js' {
-  declare module.exports: $Exports<'tcomb/lib/assign'>;
-}
-declare module 'tcomb/lib/Boolean.js' {
-  declare module.exports: $Exports<'tcomb/lib/Boolean'>;
-}
-declare module 'tcomb/lib/create.js' {
-  declare module.exports: $Exports<'tcomb/lib/create'>;
-}
-declare module 'tcomb/lib/Date.js' {
-  declare module.exports: $Exports<'tcomb/lib/Date'>;
-}
-declare module 'tcomb/lib/declare.js' {
-  declare module.exports: $Exports<'tcomb/lib/declare'>;
-}
-declare module 'tcomb/lib/decompose.js' {
-  declare module.exports: $Exports<'tcomb/lib/decompose'>;
-}
-declare module 'tcomb/lib/dict.js' {
-  declare module.exports: $Exports<'tcomb/lib/dict'>;
-}
-declare module 'tcomb/lib/enums.js' {
-  declare module.exports: $Exports<'tcomb/lib/enums'>;
-}
-declare module 'tcomb/lib/Error.js' {
-  declare module.exports: $Exports<'tcomb/lib/Error'>;
-}
-declare module 'tcomb/lib/extend.js' {
-  declare module.exports: $Exports<'tcomb/lib/extend'>;
-}
-declare module 'tcomb/lib/fail.js' {
-  declare module.exports: $Exports<'tcomb/lib/fail'>;
-}
-declare module 'tcomb/lib/forbidNewOperator.js' {
-  declare module.exports: $Exports<'tcomb/lib/forbidNewOperator'>;
-}
-declare module 'tcomb/lib/fromJSON.js' {
-  declare module.exports: $Exports<'tcomb/lib/fromJSON'>;
-}
-declare module 'tcomb/lib/func.js' {
-  declare module.exports: $Exports<'tcomb/lib/func'>;
-}
-declare module 'tcomb/lib/Function.js' {
-  declare module.exports: $Exports<'tcomb/lib/Function'>;
-}
-declare module 'tcomb/lib/getDefaultInterfaceName.js' {
-  declare module.exports: $Exports<'tcomb/lib/getDefaultInterfaceName'>;
-}
-declare module 'tcomb/lib/getFunctionName.js' {
-  declare module.exports: $Exports<'tcomb/lib/getFunctionName'>;
-}
-declare module 'tcomb/lib/getTypeName.js' {
-  declare module.exports: $Exports<'tcomb/lib/getTypeName'>;
-}
-declare module 'tcomb/lib/installTypeFormatter.js' {
-  declare module.exports: $Exports<'tcomb/lib/installTypeFormatter'>;
-}
-declare module 'tcomb/lib/Integer.js' {
-  declare module.exports: $Exports<'tcomb/lib/Integer'>;
-}
-declare module 'tcomb/lib/interface.js' {
-  declare module.exports: $Exports<'tcomb/lib/interface'>;
-}
-declare module 'tcomb/lib/intersection.js' {
-  declare module.exports: $Exports<'tcomb/lib/intersection'>;
-}
-declare module 'tcomb/lib/irreducible.js' {
-  declare module.exports: $Exports<'tcomb/lib/irreducible'>;
-}
-declare module 'tcomb/lib/is.js' {
-  declare module.exports: $Exports<'tcomb/lib/is'>;
-}
-declare module 'tcomb/lib/isArray.js' {
-  declare module.exports: $Exports<'tcomb/lib/isArray'>;
-}
-declare module 'tcomb/lib/isBoolean.js' {
-  declare module.exports: $Exports<'tcomb/lib/isBoolean'>;
-}
-declare module 'tcomb/lib/isFunction.js' {
-  declare module.exports: $Exports<'tcomb/lib/isFunction'>;
-}
-declare module 'tcomb/lib/isIdentity.js' {
-  declare module.exports: $Exports<'tcomb/lib/isIdentity'>;
-}
-declare module 'tcomb/lib/isInterface.js' {
-  declare module.exports: $Exports<'tcomb/lib/isInterface'>;
-}
-declare module 'tcomb/lib/isMaybe.js' {
-  declare module.exports: $Exports<'tcomb/lib/isMaybe'>;
-}
-declare module 'tcomb/lib/isNil.js' {
-  declare module.exports: $Exports<'tcomb/lib/isNil'>;
-}
-declare module 'tcomb/lib/isNumber.js' {
-  declare module.exports: $Exports<'tcomb/lib/isNumber'>;
-}
-declare module 'tcomb/lib/isObject.js' {
-  declare module.exports: $Exports<'tcomb/lib/isObject'>;
-}
-declare module 'tcomb/lib/isString.js' {
-  declare module.exports: $Exports<'tcomb/lib/isString'>;
-}
-declare module 'tcomb/lib/isStruct.js' {
-  declare module.exports: $Exports<'tcomb/lib/isStruct'>;
-}
-declare module 'tcomb/lib/isSubsetOf.js' {
-  declare module.exports: $Exports<'tcomb/lib/isSubsetOf'>;
-}
-declare module 'tcomb/lib/isType.js' {
-  declare module.exports: $Exports<'tcomb/lib/isType'>;
-}
-declare module 'tcomb/lib/isTypeName.js' {
-  declare module.exports: $Exports<'tcomb/lib/isTypeName'>;
-}
-declare module 'tcomb/lib/isUnion.js' {
-  declare module.exports: $Exports<'tcomb/lib/isUnion'>;
-}
-declare module 'tcomb/lib/list.js' {
-  declare module.exports: $Exports<'tcomb/lib/list'>;
-}
-declare module 'tcomb/lib/match.js' {
-  declare module.exports: $Exports<'tcomb/lib/match'>;
-}
-declare module 'tcomb/lib/maybe.js' {
-  declare module.exports: $Exports<'tcomb/lib/maybe'>;
-}
-declare module 'tcomb/lib/mixin.js' {
-  declare module.exports: $Exports<'tcomb/lib/mixin'>;
-}
-declare module 'tcomb/lib/Nil.js' {
-  declare module.exports: $Exports<'tcomb/lib/Nil'>;
-}
-declare module 'tcomb/lib/Number.js' {
-  declare module.exports: $Exports<'tcomb/lib/Number'>;
-}
-declare module 'tcomb/lib/Object.js' {
-  declare module.exports: $Exports<'tcomb/lib/Object'>;
-}
-declare module 'tcomb/lib/refinement.js' {
-  declare module.exports: $Exports<'tcomb/lib/refinement'>;
-}
-declare module 'tcomb/lib/RegExp.js' {
-  declare module.exports: $Exports<'tcomb/lib/RegExp'>;
-}
-declare module 'tcomb/lib/String.js' {
-  declare module.exports: $Exports<'tcomb/lib/String'>;
-}
-declare module 'tcomb/lib/stringify.js' {
-  declare module.exports: $Exports<'tcomb/lib/stringify'>;
-}
-declare module 'tcomb/lib/struct.js' {
-  declare module.exports: $Exports<'tcomb/lib/struct'>;
-}
-declare module 'tcomb/lib/tuple.js' {
-  declare module.exports: $Exports<'tcomb/lib/tuple'>;
-}
-declare module 'tcomb/lib/Type.js' {
-  declare module.exports: $Exports<'tcomb/lib/Type'>;
-}
-declare module 'tcomb/lib/union.js' {
-  declare module.exports: $Exports<'tcomb/lib/union'>;
-}
-declare module 'tcomb/lib/update.js' {
-  declare module.exports: $Exports<'tcomb/lib/update'>;
-}
diff --git a/lib/types/messages/media.js b/lib/types/messages/media.js
--- a/lib/types/messages/media.js
+++ b/lib/types/messages/media.js
@@ -32,16 +32,18 @@
   +media: $ReadOnlyArray<Media>,
 };
 
+export type PhotoMessageServerDBContent = {
+  +type: 'photo',
+  +uploadID: string,
+};
+export type VideoMessageServerDBContent = {
+  +type: 'video',
+  +uploadID: string,
+  +thumbnailUploadID: string,
+};
 export type MediaMessageServerDBContent =
-  | {
-      +type: 'photo',
-      +uploadID: string,
-    }
-  | {
-      +type: 'video',
-      +uploadID: string,
-      +thumbnailUploadID: string,
-    };
+  | PhotoMessageServerDBContent
+  | VideoMessageServerDBContent;
 
 function getUploadIDsFromMediaMessageServerDBContents(
   mediaMessageContents: $ReadOnlyArray<MediaMessageServerDBContent>,
diff --git a/lib/utils/avatar-utils.js b/lib/utils/avatar-utils.js
--- a/lib/utils/avatar-utils.js
+++ b/lib/utils/avatar-utils.js
@@ -6,32 +6,41 @@
 import { tRegex, tShape, tString } from './validation-utils.js';
 import { validHexColorRegex } from '../shared/account-utils.js';
 import { onlyOneEmojiRegex } from '../shared/emojis.js';
-
-const emojiAvatarDBContentValidator: TInterface = tShape({
+import type {
+  ENSAvatarDBContent,
+  EmojiAvatarDBContent,
+  ImageAvatarDBContent,
+  UpdateUserAvatarRemoveRequest,
+  UpdateUserAvatarRequest,
+} from '../types/avatar-types';
+
+const emojiAvatarDBContentValidator: TInterface<EmojiAvatarDBContent> = tShape({
   type: tString('emoji'),
   emoji: tRegex(onlyOneEmojiRegex),
   color: tRegex(validHexColorRegex),
 });
 
-const imageAvatarDBContentValidator: TInterface = tShape({
+const imageAvatarDBContentValidator: TInterface<ImageAvatarDBContent> = tShape({
   type: tString('image'),
   uploadID: t.String,
 });
 
-const ensAvatarDBContentValidator: TInterface = tShape({
+const ensAvatarDBContentValidator: TInterface<ENSAvatarDBContent> = tShape({
   type: tString('ens'),
 });
 
-const updateUserAvatarRemoveRequestValidator: TInterface = tShape({
-  type: tString('remove'),
-});
-
-const updateUserAvatarRequestValidator: TUnion<TInterface> = t.union([
-  emojiAvatarDBContentValidator,
-  imageAvatarDBContentValidator,
-  ensAvatarDBContentValidator,
-  updateUserAvatarRemoveRequestValidator,
-]);
+const updateUserAvatarRemoveRequestValidator: TInterface<UpdateUserAvatarRemoveRequest> =
+  tShape({
+    type: tString('remove'),
+  });
+
+const updateUserAvatarRequestValidator: TUnion<UpdateUserAvatarRequest> =
+  t.union([
+    emojiAvatarDBContentValidator,
+    imageAvatarDBContentValidator,
+    ensAvatarDBContentValidator,
+    updateUserAvatarRemoveRequestValidator,
+  ]);
 
 export {
   emojiAvatarDBContentValidator,
diff --git a/lib/utils/crypto-utils.js b/lib/utils/crypto-utils.js
--- a/lib/utils/crypto-utils.js
+++ b/lib/utils/crypto-utils.js
@@ -5,20 +5,26 @@
 
 import { primaryIdentityPublicKeyRegex } from './siwe-utils.js';
 import { tRegex, tShape } from './validation-utils.js';
+import type {
+  IdentityKeysBlob,
+  OLMIdentityKeys,
+  SignedIdentityKeysBlob,
+} from '../types/crypto-types';
 
 const minimumOneTimeKeysRequired = 10;
 
-const signedIdentityKeysBlobValidator: TInterface = tShape({
-  payload: t.String,
-  signature: t.String,
-});
+const signedIdentityKeysBlobValidator: TInterface<SignedIdentityKeysBlob> =
+  tShape({
+    payload: t.String,
+    signature: t.String,
+  });
 
-const olmIdentityKeysValidator: TInterface = tShape({
+const olmIdentityKeysValidator: TInterface<OLMIdentityKeys> = tShape({
   ed25519: tRegex(primaryIdentityPublicKeyRegex),
   curve25519: tRegex(primaryIdentityPublicKeyRegex),
 });
 
-const identityKeysBlobValidator: TInterface = tShape({
+const identityKeysBlobValidator: TInterface<IdentityKeysBlob> = tShape({
   primaryIdentityPublicKeys: olmIdentityKeysValidator,
   notificationIdentityPublicKeys: olmIdentityKeysValidator,
 });
diff --git a/lib/utils/validation-utils.js b/lib/utils/validation-utils.js
--- a/lib/utils/validation-utils.js
+++ b/lib/utils/validation-utils.js
@@ -15,6 +15,12 @@
   oldValidUsernameRegex,
   validHexColorRegex,
 } from '../shared/account-utils.js';
+import type { PlatformDetails } from '../types/device-types';
+import type {
+  MediaMessageServerDBContent,
+  PhotoMessageServerDBContent,
+  VideoMessageServerDBContent,
+} from '../types/messages/media';
 
 function tBool(value: boolean): TIrreducible<boolean> {
   return t.irreducible('literal bool', x => x === value);
@@ -28,7 +34,7 @@
   return t.irreducible('literal number', x => x === value);
 }
 
-function tShape(spec: TStructProps): TInterface {
+function tShape<T>(spec: TStructProps<T>): TInterface<T> {
   return t.interface(spec, { strict: true });
 }
 
@@ -58,7 +64,7 @@
   'macos',
 ]);
 const tDeviceType: TEnums = t.enums.of(['ios', 'android']);
-const tPlatformDetails: TInterface = tShape({
+const tPlatformDetails: TInterface<PlatformDetails> = tShape({
   platform: tPlatform,
   codeVersion: t.maybe(t.Number),
   stateVersion: t.maybe(t.Number),
@@ -72,18 +78,18 @@
 const tOldValidUsername: TRegex = tRegex(oldValidUsernameRegex);
 const tID: TRefinement<string> = t.refinement(t.String, (id: string) => !!id);
 
-const tMediaMessagePhoto: TInterface = tShape({
+const tMediaMessagePhoto: TInterface<PhotoMessageServerDBContent> = tShape({
   type: tString('photo'),
   uploadID: t.String,
 });
 
-const tMediaMessageVideo: TInterface = tShape({
+const tMediaMessageVideo: TInterface<VideoMessageServerDBContent> = tShape({
   type: tString('video'),
   uploadID: t.String,
   thumbnailUploadID: t.String,
 });
 
-const tMediaMessageMedia: TUnion<TInterface> = t.union([
+const tMediaMessageMedia: TUnion<MediaMessageServerDBContent> = t.union([
   tMediaMessagePhoto,
   tMediaMessageVideo,
 ]);