Change your cities function to use the data property of the response in your .then (that's how you'll access the response from a resolved HttpPromise):
var plunker= angular.module('plunker', ['ui.bootstrap', 'ngGrid']);
function TypeaheadCtrl($scope, $window, $http, limitToFilter) {
$scope.cities = function (cityName) {
return $http.get("http://mtapi.azurewebsites.net/api/institute").then(function (response) {
return response.data[0].description;
});
};
EDIT
Even making that code change won't solve your problem. This url does not support cross-origin requests, so you either need to host your angularjs app on the same domain and use a plain $http.get instead of $http.jsonp, or this url needs to support JSONP requests (the content-type of the response from this url is application/json. For JSONP to work it should be application/javascript).