diff --git a/src/input-types.js b/src/input-types.js
index a676003d..aae18f3c 100644
--- a/src/input-types.js
+++ b/src/input-types.js
@@ -156,11 +156,13 @@ function defineType(info) {
 
   let baseParamsMeta = null;
   let getParams = () => undefined;
+  const getMeta = (params) =>
+    Array.isArray(params) ? params : Object.keys(params);
   if (typeof (info.baseParams) === "object") {
     getParams = () => info.baseParams;
-    baseParamsMeta = Array.isArray(info.baseParams)
-      ? info.baseParams
-      : Object.keys(info.baseParams);
+    if (!(info.baseParams instanceof Promise)) {
+      baseParamsMeta = getMeta(info.baseParams);
+    }
   } else if (typeof (info.baseParams) === "function") {
     getParams = info.baseParams;
   } else if (info.baseParams) {
@@ -177,6 +179,13 @@ function defineType(info) {
       params: baseParamsMeta,
     },
   };
+  // promises get late linking into the type metadata
+  if (info.baseParams instanceof Promise) {
+    (async () => {
+      typeMeta.baseType.params = getMeta(await info.baseParams);
+    })();
+  }
+
   const argType = new RPCArgumentType(
     info.name,
     typeMeta,
diff --git a/src/procedures/translation/translation.js b/src/procedures/translation/translation.js
index e9e0306c..a647c4af 100644
--- a/src/procedures/translation/translation.js
+++ b/src/procedures/translation/translation.js
@@ -8,6 +8,7 @@
  */
 
 const { AzureTranslationKey } = require("../utils/api-key");
+const types = require("../../input-types");
 const ApiConsumer = require("../utils/api-consumer");
 const TranslationConsumer = new ApiConsumer(
   "Translation",
@@ -16,6 +17,25 @@ const TranslationConsumer = new ApiConsumer(
 );
 ApiConsumer.setRequiredApiKey(TranslationConsumer, AzureTranslationKey);
 
+let SUPPORTED_LANGUAGES = undefined;
+types.defineType({
+  name: "Language",
+  description:
+    "A language supported by the :doc:`/services/Translation/index` service.",
+  baseType: "Enum",
+  baseParams: (async () => {
+    SUPPORTED_LANGUAGES = (await TranslationConsumer._requestData({
+      path: "languages",
+      queryString: "?api-version=3.0&scope=translation",
+      headers: {
+        "Content-Type": "application/json",
+        "Ocp-Apim-Subscription-Key": TranslationConsumer.apiKey.value,
+      },
+    })).translation;
+    return Object.keys(SUPPORTED_LANGUAGES);
+  })(),
+});
+
 /**
  * Generates a GUID-like string
  */
@@ -29,8 +49,8 @@ TranslationConsumer._get_guid = function () {
 /**
  * Translate text between languages
  * @param {String} text Text in another language
- * @param {String=} from Language to translate from (auto-detects if not specified)
- * @param {String} to Language to translate to
+ * @param {Language=} from Language to translate from (auto-detects if not specified)
+ * @param {Language} to Language to translate to
  * @returns {String} Text translated to requested language
  */
 TranslationConsumer.translate = function (text, from, to) {
@@ -70,7 +90,7 @@ TranslationConsumer.toEnglish = function (text) {
 /**
  * Attempt to detect language of input text
  * @param {String} text Text in an unknown language
- * @returns {String} Abbreviation for name of language detected in text
+ * @returns {Language} Abbreviation for name of language detected in text
  */
 TranslationConsumer.detectLanguage = function (text) {
   let body = [{ "Text": text }];
@@ -93,20 +113,10 @@ TranslationConsumer.detectLanguage = function (text) {
 
 /**
  * Attempt to detect language of input text
- * @returns {Array} List of languages supported by the translator
+ * @returns {Object} List of languages supported by the translator
  */
 TranslationConsumer.getSupportedLanguages = function () {
-  return this._sendAnswer({
-    path: "languages",
-    queryString: "?api-version=3.0&scope=translation",
-    headers: {
-      "Content-Type": "application/json",
-      "Ocp-Apim-Subscription-Key": this.apiKey.value,
-    },
-  }, ".translation")
-    .catch((err) => {
-      throw err;
-    });
+  return SUPPORTED_LANGUAGES;
 };
 
 module.exports = TranslationConsumer;