If you're a city employee who deals with the public—at the traffic and parking counter, the library or elsewhere—be advised: The residents you help could be secret, undercover agents working for the city.

That's because Somerville is looking for "mystery customers" to test city services beginning this summer. It's part of an ongoing effort to "evaluate how well the entire system is working," said Michael Meehan, spokesperson for the city of Somerville.

The city is hoping to get about 15 or 20 Somerville residents to become mystery customers. They won't be paid, and their identities will never be shared with the public or city departments. But they will receive small thank-you gifts, such as Somerville tote bags or coffee mugs, for their services.

(Note to the city clerk's office: If a woman walks up to your counter with a Somerville-branded tote bag, drinking chai latte out of a Somerville-branded mug, and asks for a dog license, she could be a mystery customer. Or maybe she's a decoy. In this game of cat and mouse, you never know who's on your team and who's not.)

Meehan said Somerville is filled with "talented, civic-minded people," and those are exactly the sort of people the city wants to participate in the mystery customer program.

Those interested in participating should sign up with the city's ResiStat program. The city will ask potential participants a few questions to make sure they have what it takes to be a mystery customer. Those who join this elite force will be able to fill out evaluations online or through a phone survey.

Meehan said that to his knowledge, Somerville has never conducted mystery customer surveys before, but it's something the private sector does all the time.

"If you were running a company, this is something you'd do in the normal course of business," he said. In this case, "the taxpayers are your customers."

While the mystery customer initiative is scheduled to begin this summer, it will continue as an ongoing program, said Meehan. The city is conducting the survey in-house and is not using outside consultants, he said.

Those interested in becoming mystery customers can sign up online at somevilleresistat.blogspot.com, or they can contact Denise Taylor, ResiStat coordinator, at 617-625-6600 ext. 2103 or at dtaylor@somervillema.gov.

Note: Taylor, Somerville's ResiStat coordinator, is the former editor of Somerville Patch.