After months of saying that improvements were coming to its search engine, Twitter has announced a small but critical upgrade. In a blog post, Twitter says it has started an experiment that will “show higher quality results for trend queries by returning tweets that are more useful.” No details on how that will be determined, but it suggests that Twitter will incorporate the relevancy of a Tweet when users search for a term; right now, Twitter only returns a list of Tweets based on when they were sent.

Twitter cautions that the “improvement won’t be very noticeable at first”—but considering that its search function may be the most monetizable aspect of its service yet is currently so limited it’s important. And the microblogging service implies that it’s the beginning of a longer list of upgrades, saying in the post that “this is a small step toward unearthing more value in search and getting you more relevant results.”

This also comes as both Google (NSDQ: GOOG) and Microsoft (NSDQ: MSFT) will now have full access to Twitter’s stream of data—and therefore will be able to add new ways to search through Tweets, in addition to what Twitter offers. Already, Microsoft is giving users the option to search not just by when Tweets are posted, but also by “best match” which the company says takes into account factors including the popularity of the Tweeter.

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