diff --git a/lib/client.js b/lib/client.js
index afbb1b0c8..834f740c0 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -2788,7 +2788,7 @@ MatrixClient.prototype.register = function(username, password,
 /**
  * Requests an email verification token for the purposes of registration.
  * This API proxies the Identity Server /validate/email/requestToken API,
- * adding registration-specific behaviour. Specifically, an account with
+ * adding registration-specific behaviour. Specifically, if an account with
  * the given email address already exists, it will either send an email
  * to the address informing them of this or return M_THREEPID_IN_USE
  * (which one is up to the Home Server).
@@ -2796,17 +2796,14 @@ MatrixClient.prototype.register = function(username, password,
  * requestEmailToken calls the equivalent API directly on the ID server,
  * therefore bypassing the registration-specific logic.
  *
- * @param {string} email
- * @param {string} clientSecret
- * @param {string} sendAttempt
- * @param {string} nextLink Optional
- * @param {module:client.callback} callback Optional.
- * @return {module:client.Promise} Resolves: TODO
- * @return {module:http-api.MatrixError} Rejects: with an error response.
+ * Parameters and return value are as for requestEmailToken
  */
 MatrixClient.prototype.requestRegisterEmailToken = function(email, clientSecret,
                                                     sendAttempt, nextLink, callback) {
     var id_server_url = url.parse(this.idBaseUrl);
+    if (id_server_url.host == null) {
+        throw new Error("Invalid ID server URL: " + this.idBaseUrl);
+    }
 
     var params = {
         client_secret: clientSecret,
@@ -3707,13 +3704,19 @@ MatrixClient.prototype.getEventMapper = function() {
  * Note that the Home Server offers APIs to proxy this API for specific
  * situations, allowing for better feedback to the user.
  *
- * @param {string} email
- * @param {string} clientSecret
- * @param {string} sendAttempt
- * @param {string} nextLink Optional
+ * @param {string} email The email address to request a token for
+ * @param {string} clientSecret A secret binary string generated by the client.
+ *                 It is recommended this be around 16 ASCII characters.
+ * @param {number} sendAttempt If an identity server sees a duplicate request
+ *                 with the same sendAttempt, it will not send another email.
+ *                 To request another email to be sent, use a larger value for
+ *                 the sendAttempt param as was used in the previous request.
+ * @param {string} nextLink Optional If specified, the client will be redirected
+ *                 to this link after validation.
  * @param {module:client.callback} callback Optional.
  * @return {module:client.Promise} Resolves: TODO
  * @return {module:http-api.MatrixError} Rejects: with an error response.
+ * @throws Error if No ID server is set
  */
 MatrixClient.prototype.requestEmailToken = function(email, clientSecret,
                                                     sendAttempt, nextLink, callback) {