diff --git a/keyserver/src/uploads/uploads.js b/keyserver/src/uploads/uploads.js
--- a/keyserver/src/uploads/uploads.js
+++ b/keyserver/src/uploads/uploads.js
@@ -4,16 +4,17 @@
 import invariant from 'invariant';
 import multer from 'multer';
 import { Readable } from 'stream';
-import t from 'tcomb';
+import t, { type TInterface } from 'tcomb';
 
-import type {
-  UploadMediaMetadataRequest,
-  UploadMultimediaResult,
-  UploadDeletionRequest,
-  Dimensions,
+import {
+  type UploadMediaMetadataRequest,
+  type UploadMultimediaResult,
+  uploadMultimediaResultValidator,
+  type UploadDeletionRequest,
+  type Dimensions,
 } from 'lib/types/media-types.js';
 import { ServerError } from 'lib/utils/errors.js';
-import { tShape } from 'lib/utils/validation-utils.js';
+import { tShape, tID } from 'lib/utils/validation-utils.js';
 
 import { getMediaType, validateAndConvert } from './media-utils.js';
 import type { UploadInput } from '../creators/upload-creator.js';
@@ -26,7 +27,7 @@
 } from '../fetchers/upload-fetchers.js';
 import type { MulterRequest } from '../responders/handlers.js';
 import type { Viewer } from '../session/viewer.js';
-import { validateInput } from '../utils/validation-utils.js';
+import { validateInput, validateOutput } from '../utils/validation-utils.js';
 
 const upload = multer();
 const multerProcessor: Middleware<> = upload.array('multimedia');
@@ -34,6 +35,10 @@
 type MultimediaUploadResult = {
   results: UploadMultimediaResult[],
 };
+const MultimediaUploadResultValidator = tShape<MultimediaUploadResult>({
+  results: t.list(uploadMultimediaResultValidator),
+});
+
 async function multimediaUploadResponder(
   viewer: Viewer,
   req: MulterRequest,
@@ -97,10 +102,16 @@
     throw new ServerError('invalid_parameters');
   }
   const results = await createUploads(viewer, uploadInfos);
-  return { results };
+  return validateOutput(
+    viewer.platformDetails,
+    MultimediaUploadResultValidator,
+    {
+      results,
+    },
+  );
 }
 
-const uploadMediaMetadataInputValidator = tShape({
+const uploadMediaMetadataInputValidator = tShape<UploadMediaMetadataRequest>({
   filename: t.String,
   width: t.Number,
   height: t.Number,
@@ -113,10 +124,13 @@
 
 async function uploadMediaMetadataResponder(
   viewer: Viewer,
-  input: any,
+  input: mixed,
 ): Promise<UploadMultimediaResult> {
-  const request: UploadMediaMetadataRequest = input;
-  await validateInput(viewer, uploadMediaMetadataInputValidator, input);
+  const request = await validateInput(
+    viewer,
+    uploadMediaMetadataInputValidator,
+    input,
+  );
 
   const mediaType = getMediaType(request.mimeType);
   if (!mediaType) {
@@ -137,7 +151,11 @@
   };
 
   const [result] = await createUploads(viewer, [uploadInfo]);
-  return result;
+  return validateOutput(
+    viewer.platformDetails,
+    uploadMultimediaResultValidator,
+    result,
+  );
 }
 
 async function uploadDownloadResponder(
@@ -206,11 +224,20 @@
   }
 }
 
+const uploadDeletionRequestInputValidator: TInterface<UploadDeletionRequest> =
+  tShape<UploadDeletionRequest>({
+    id: tID,
+  });
 async function uploadDeletionResponder(
   viewer: Viewer,
-  request: UploadDeletionRequest,
+  input: mixed,
 ): Promise<void> {
-  const { id } = request;
+  const { id } = await validateInput(
+    viewer,
+    uploadDeletionRequestInputValidator,
+    input,
+  );
+
   await deleteUpload(viewer, id);
 }
 
diff --git a/lib/types/media-types.js b/lib/types/media-types.js
--- a/lib/types/media-types.js
+++ b/lib/types/media-types.js
@@ -17,6 +17,7 @@
 });
 
 export type MediaType = 'photo' | 'video';
+const mediaTypeValidator = t.enums.of(['photo', 'video']);
 
 export type EncryptedMediaType = 'encrypted_photo' | 'encrypted_video';
 
@@ -64,6 +65,14 @@
   +mediaType: MediaType,
   +loop: boolean,
 };
+export const uploadMultimediaResultValidator: TInterface<UploadMultimediaResult> =
+  tShape<UploadMultimediaResult>({
+    id: tID,
+    uri: t.String,
+    dimensions: dimensionsValidator,
+    mediaType: mediaTypeValidator,
+    loop: t.Boolean,
+  });
 
 export type UpdateMultimediaMessageMediaPayload = {
   +messageID: string,