diff --git a/bin/generate-api b/bin/generate-api
index bebeea5e3..5af66eafe 100755
--- a/bin/generate-api
+++ b/bin/generate-api
@@ -26,9 +26,8 @@ module Google
     Discovery = Google::Apis::DiscoveryV1
 
     desc 'gen OUTDIR', 'Generate ruby API from an API description'
-    method_options url: :array, file: :array, from_discovery: :boolean, id: :array,
-                   preferred_only: :boolean, verbose: :boolean, names: :string,
-                   names_out: :string
+    method_options url: :array, file: :array, from_discovery: :boolean, preferred_only: :boolean,
+                   verbose: :boolean, names: :string, names_out: :string
     method_option :preferred_only, default: true
     def gen(dir)
       ensure_active_support
@@ -38,7 +37,7 @@ module Google
       Google::Apis.logger.level = Logger::DEBUG if options[:verbose]
       generate_from_url(options[:url]) if options[:url]
       generate_from_file(options[:file]) if options[:file]
-      generate_from_discovery(preferred_only: options[:preferred_only], id: options[:id] ) if options[:id] || options[:from_discovery]
+      generate_from_discovery(preferred_only: options[:preferred_only]) if options[:from_discovery]
       create_file(options[:names_out]) { |*| generator.dump_api_names } if options[:names_out]
     end
 
@@ -69,16 +68,22 @@ module Google
         end
       end
 
-      def generate_from_discovery(preferred_only: false, id: nil)
+      def generate_from_discovery(preferred_only: false)
         say 'Fetching API list'
-        id = Array(id)
         apis = discovery.list_apis
         apis.items.each do |api|
-          if (id.empty? && preferred_only && api.preferred?) || id.include?(api.id)
-            say sprintf('Loading %s, version %s from %s', api.name, api.version, api.discovery_rest_url)
-            generate_from_url(api.discovery_rest_url)
-          else
+          if (preferred_only && !api.preferred?)
             say sprintf('Ignoring disoverable API %s', api.id)
+          else
+	    # The Discovery service may returned cached versions of a Discovery document that are
+	    # not the most recent revision. That means that subsequent requests to the same
+	    # Discovery document URL can return different documents. The
+	    # `discovery-artifact-manager` repo always holds the most recent revision, so it's
+	    # easier to use that document than to force revision checking against the URL returned
+	    # by the Discovery index.
+            discovery_rest_url = "https://raw.githubusercontent.com/googleapis/discovery-artifact-manager/master/discoveries/#{api.name}.#{api.version}.json"
+            say sprintf('Loading %s, version %s from %s', api.name, api.version, discovery_rest_url)
+            generate_from_url(discovery_rest_url)
           end
         end
       end
diff --git a/script/generate b/script/generate
index 751af0899..1d8891d84 100755
--- a/script/generate
+++ b/script/generate
@@ -4,134 +4,6 @@
 
 DIR=$(dirname $( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd ))
 
-API_IDS=(acceleratedmobilepageurl:v1 \
-  adexchangebuyer:v1.4 \
-  adexchangebuyer2:v2beta1 \
-  adexchangeseller:v2.0 \
-  admin:directory_v1 \
-  admin:datatransfer_v1 \
-  admin:reports_v1 \
-  adsense:v1.4 \
-  adsensehost:v4.1 \
-  analytics:v3 \
-  analyticsreporting:v4 \
-  androidenterprise:v1 \
-  androidpublisher:v2 \
-  appengine:v1 \
-  appsactivity:v1 \
-  appsmarket:v2 \
-  appstate:v1 \
-  autoscaler:v1beta2 \
-  bigquery:v2 \
-  blogger:v3 \
-  books:v1 \
-  calendar:v3 \
-  civicinfo:v2 \
-  classroom:v1 \
-  cloudbilling:v1 \
-  cloudbuild:v1 \
-  clouddebugger:v2 \
-  clouderrorreporting:v1beta1 \
-  cloudfunctions:v1 \
-  cloudkms:v1 \
-  cloudkms:v1beta1 \
-  cloudlatencytest:v2 \
-  cloudmonitoring:v2beta2 \
-  cloudresourcemanager:v1beta1 \
-  cloudresourcemanager:v1 \
-  cloudtrace:v1 \
-  clouduseraccounts:beta \
-  compute:v1 \
-  compute:beta \
-  container:v1 \
-  content:v2 \
-  coordinate:v1 \
-  customsearch:v1 \
-  dataflow:v1b3 \
-  dataproc:v1 \
-  datastore:v1 \
-  deploymentmanager:v2 \
-  dfareporting:v2.6 \
-  dfareporting:v2.7 \
-  dfareporting:v2.8 \
-  discovery:v1 \
-  dns:v1 \
-  dns:v2beta1 \
-  doubleclickbidmanager:v1 \
-  doubleclicksearch:v2 \
-  drive:v2 \
-  drive:v3 \
-  firebasedynamiclinks:v1 \
-  firebaserules:v1 \
-  fitness:v1 \
-  fusiontables:v2 \
-  games:v1 \
-  gamesConfiguration:v1configuration \
-  gamesManagement:v1management \
-  gan:v1beta1 \
-  genomics:v1 \
-  gmail:v1 \
-  groupsmigration:v1 \
-  groupssettings:v1 \
-  iam:v1 \
-  identitytoolkit:v3 \
-  kgsearch:v1 \
-  language:v1beta1 \
-  language:v1 \
-  licensing:v1 \
-  logging:v2beta1 \
-  logging:v2 \
-  manager:v1beta2 \
-  manufacturers:v1 \
-  mapsengine:v1 \
-  mirror:v1 \
-  ml:v1 \
-  oauth2:v2 \
-  pagespeedonline:v2 \
-  partners:v2 \
-  people:v1 \
-  plus:v1 \
-  plusDomains:v1 \
-  prediction:v1.6 \
-  proximitybeacon:v1beta1 \
-  pubsub:v1 \
-  qpxExpress:v1 \
-  replicapool:v1beta2 \
-  replicapoolupdater:v1beta1 \
-  reseller:v1 \
-  resourceviews:v1beta2 \
-  runtimeconfig:v1 \
-  script:v1 \
-  searchconsole:v1 \
-  servicecontrol:v1 \
-  servicemanagement:v1 \
-  serviceuser:v1 \
-  sheets:v4 \
-  siteVerification:v1 \
-  slides:v1 \
-  sourcerepo:v1 \
-  spanner:v1 \
-  speech:v1beta1 \
-  sqladmin:v1beta4 \
-  storage:v1 \
-  storagetransfer:v1 \
-  surveys:v2 \
-  tagmanager:v1 \
-  tagmanager:v2 \
-  taskqueue:v1beta2 \
-  tasks:v1 \
-  toolresults:v1beta3 \
-  tracing:v1 \
-  translate:v2 \
-  urlshortener:v1 \
-  vision:v1 \
-  webfonts:v1 \
-  webmasters:v3 \
-  youtube:v3 \
-  youtubeAnalytics:v1 \
-  youtubereporting:v1 \
-)
-
 URLS=(https://content.googleapis.com/discovery/v1/apis/appsmarket/v2/rest \
       https://content.googleapis.com/discovery/v1/apis/youtubePartner/v1/rest \
       https://content.googleapis.com/discovery/v1/apis/compute/beta/rest \
@@ -139,4 +11,4 @@ URLS=(https://content.googleapis.com/discovery/v1/apis/appsmarket/v2/rest \
       https://monitoring.googleapis.com/\$discovery/rest?version=v3 \
 )
 
-echo 'a' | bundle exec bin/generate-api gen generated --from_discovery=true --names_out=$DIR/api_names_out.yaml --url=${URLS[*]}  --id=${API_IDS[*]}
+echo 'a' | bundle exec bin/generate-api gen generated --from_discovery=true --names_out=$DIR/api_names_out.yaml --url=${URLS[*]}