Microsoft has introduced a reporting tool for its online advertising platform that it claims measures the impact of online ad campaigns rather than merely counting clicks.

The tool, called Engagement ROI, has been integrated into Microsoft's Atlas Media Console, which is software used for booking and managing online advertising campaigns. A senior Microsoft executive will officially announce the tool on Monday at the Interactive Advertising Bureau's annual meeting in Phoenix.

The Media Console was developed by Atlas, a company that was owned by aQuantive, which Microsoft bought for $6 billion in May 2007. It marked Microsoft's biggest acquisition in the online advertising space, following Google's announcement in April 2007 of its intention to acquire a rival online advertising firm, DoubleClick.

Google has a huge lead over Microsoft in online advertising. To counter Google's dominance, Microsoft made an unsolicited offer earlier this month to buy Yahoo, but the acquisition has been so far resisted by Yahoo's board. Microsoft wants access to Yahoo's engineers as well as the company's online advertising technology.

Engagement ROI is in a beta release. Microsoft said the tool will undergo testing with national advertising agencies such as McKinney, Mindshare Interaction, World Vision, and Neo@Ogilvy.

Engagement ROI looks at several aspects of an online ad, such as how recently it has been displayed, its size and its format, and then determines how successful the message is in influencing a purchase. Microsoft calls the concept "engagement mapping."

Microsoft said the most commonly used metric in the industry, counting clicks, is a poor way to measure the effectiveness of an ad campaign. Generally, the success of an ad is determined on how frequently it is viewed or clicked.

Microsoft expects to begin receiving results on how successful the tool is by the end of June.