diff --git a/keyserver/src/socket/socket.js b/keyserver/src/socket/socket.js
--- a/keyserver/src/socket/socket.js
+++ b/keyserver/src/socket/socket.js
@@ -15,7 +15,7 @@
 } from 'lib/shared/timeouts.js';
 import { mostRecentUpdateTimestamp } from 'lib/shared/update-utils.js';
 import { hasMinCodeVersion } from 'lib/shared/version-utils.js';
-import { endpointIsSocketSafe } from 'lib/types/endpoints.js';
+import { endpointIsSocketSafe, endpoints } from 'lib/types/endpoints.js';
 import { redisMessageTypes, type RedisMessage } from 'lib/types/redis-types.js';
 import {
   serverRequestTypes,
@@ -126,7 +126,7 @@
     ),
     id: t.Number,
     payload: tShape({
-      endpoint: t.String,
+      endpoint: t.enums.of(endpoints),
       input: t.maybe(t.Object),
     }),
   }),
diff --git a/lib/types/endpoints.js b/lib/types/endpoints.js
--- a/lib/types/endpoints.js
+++ b/lib/types/endpoints.js
@@ -1,5 +1,7 @@
 // @flow
 
+import { values } from '../utils/objects.js';
+
 export type APIRequest = {
   endpoint: Endpoint,
   input?: Object,
@@ -144,3 +146,11 @@
 export function endpointIsSocketOnly(endpoint: Endpoint): boolean {
   return socketOnlyEndpointSet.has(endpoint);
 }
+
+export const endpoints: $ReadOnlyArray<Endpoint> = [
+  ...values(sessionChangingEndpoints),
+  ...values(uploadEndpoints),
+  ...values(largeDataFetchEndpoints),
+  ...values(socketOnlyEndpoints),
+  ...values(httpPreferredEndpoints),
+];