The new Redfin app for Microsoft’s Windows Phone promises to deliver the core features of the online real estate service, including the ability to search for homes to rent or buy, research neighborhoods, and find an agent. But unlike Redfin’s 4.5-star apps for iPhone and Android, this app gets a 2.5-star rating, and a string of negative reviews.

“Mediocre experience at best,” says one reviewer. “Please get the real app.”

As it turns out, this isn’t a native Windows Phone app — and it wasn’t made by Redfin. It was developed by Microsoft, by packaging up Redfin’s mobile website in the form of an installable app.

In fact, the existence of the Redfin app for Windows Phone was a surprise to Redfin.

“Redfin did not authorize Microsoft to do this,” said Redfin spokeswoman Jani Strand in an email to GeekWire today.

Redfin is far from alone in experiencing Microsoft’s web-app wrapup. This is part of a broader initiative by the Redmond company to stock its app store with more of the popular services that consumers have come to expect on smartphones. There are more than 80 apps associated with the Microsoft WebApps account on the Windows Phone Store at the moment — including notable brands such as Trulia, Lowe’s, Meetup, Coach, Ugg, Jimmy John’s, Orbitz, and many more.

The initiative dates back to the fall, when Southwest Airlines asked Microsoft to remove its unauthorized web app, developed by Microsoft, from the Windows Phone Store. Microsoft complied with that request, but the overall initiative has continued, with one of the web apps, for the TOMS shoes and eyewear site, published as recently as yesterday. The Redfin app was published last week.

Responding to an inquiry from GeekWire today, Microsoft said the reception for the web apps overall has been positive. The idea, the company says, is to give Windows Phone users “quick pinnable access to select mobile websites that work great on Windows Phone.”

The company said in a statement, “Customer response to WebApps has been strong with an average user rating of more than 4 of 5 stars, prompting several companies to take ownership of a WebApp and republish it themselves.”

Microsoft’s statement continued, “We’ve found that the majority of site owners appreciate the fact that WebApps engage more people in the company’s own website experience; however, we are happy to work with content owners to resolve any concerns they may have. Website owners are welcome to contact us at wpwebapps@microsoft.com.”

The push reflects the pressure that Microsoft is under to bolster the Windows Phone Store, and make Windows Phone more attractive to users. The company has succeeded in landing many big-name apps, including Instagram and Waze last fall, but most developers still target iPhone and Android first. Windows Phone has moved into third place in worldwide market share, by some measures, but remains well behind its larger rivals, reducing the potential market for app developers.

It is true that the majority of the WebApps on Microsoft’s official account have an average rating above 4 stars, but almost 82 percent of all the WebApps published have 5 or fewer ratings. 33 of those apps haven’t been rated at all, and only one app has more than 25 reviews. Lowe’s, the sole outlier, has 72 reviews and a five star average, but that isn’t many reviews compared to the most popular apps, which often have hundreds or thousands of ratings.

In the case of Redfin, company spokeswoman Strand said that the description of its Windows Phone app isn’t “accurate or precise.” While the app’s description claims that users can search for homes to rent, for example, Redfin does not handle rental properties.

As it turns out, the Redfin app shares its description almost word-for-word with Trulia’s Windows Phone WebApp. In the case of both companies, Microsoft did not ask for their permission before creating a web app for them.

Reviews for both apps are filled with complaints about malfunctions, errors, and just the fact that the apps only redirect to a website, rather than serving as a complete native experience. That’s a common thread among all of the most-reviewed web apps from Microsoft: A number of users are disappointed with bugs and missing functionality.

“I’ll just stick with zillow,” says one reviewer of the Trulia app, after complaining that 99% of the homes in the app have a value of N/A. (Zillow, in fact, does have a native Windows Phone app — made by Zillow — although it hasn’t been updated in a year-and-a-half.)

Because the companies whose brands are represented by these apps are initially unaware of their existence, it can be hard for them to fix problems that users are having, leading to more negative reviews.

The apps are identified as web apps in their Windows Phone Store descriptions, and the publisher is listed as “Microsoft WebApps.” Clicking on the “show details” link in the Redfin description reveals this disclaimer, “Microsoft does not claim ownership of or responsibility for the content in this app. This app links directly to content available at http://redfin.com/.”

But the fact that they aren’t native apps can be easily overlooked by people quickly downloading them, and in many cases end users might not even make that distinction.

Microsoft said in its statement, “Windows Phone WebApps are developed by Microsoft to enable access to existing third party web-based resources. Windows Phone WebApps are not a replacement for full featured native applications.”

There could be good news on the horizon for companies that don’t want to spend time developing a Windows Phone app. A report surfaced last week claiming that Microsoft is investigating the possibility of letting users run Android apps on Windows Phone.

Redfin declined to say how it plans to handle its Windows Phone surprise. Trulia says it’s contacting Microsoft about the situation.