The US is looking to buy software that can identify sarcasm on social media so that it can distinguish between actual threats and ill-advised jokes.
United States government agencies and corporations have long used social media to try to get their messages out, while law-enforcement agencies increasingly monitor such sites for signs of trouble.
However, getting a computer to detect sarcasm and its linguistic complexities can be difficult, and some experts worry about attempts to interpret speech by a government agency that has the power to arrest people for posting alleged threats online.
"It does appear that it's going to be a pretty broad monitoring programme. It will likely sweep in some First Amendment-protected expression," said Ginger McCall, associate director of the Electronic Privacy Information Centre.
"It is troubling, because it really stifles people's ability to freely express themselves and it has a tendency to quell dissent to make people think twice before they express themselves online."
The Secret Service request for the software, first reported by nextgov.com  was posted on Monday. The agency is accepting proposals until next Monday.
The work order asks for a long list of specific tools, including the ability to identify influential figures on social media, analyse data streams instantly and access old social-media data.
Secret Service spokesman Ed Donovan said the request would allow the agency to create its own system for monitoring Twitter, and detecting sarcasm was just a small feature of the effort.
"Our objective is to automate our social-media monitoring process," he said. "Twitter is what we analyse. This is real-time stream analysis. The ability to detect sarcasm and false positives is just one of 16 or 18 things we are looking at."
Companies already used algorithms that attempted to detect sarcasm online or over the telephone in measuring things such as customer satisfaction, said Lisa Sotto, a managing partner of Hunton and Williams in New York, who focuses on issues involving cybersecurity.
Peter Eckersley, technology projects director for the Electronic Frontier Foundation, thinks the Secret Service effort will fail because computers can't grasp the nuances of language.
"It's difficult not to be sarcastic about the idea of the Secret Service automatically, algorithmically, examining all of your social media posts to determine, among other things, that you're being sarcastic," he said.
A Texas teenager was arrested last year after posting what he said was a sarcastic comment about shooting up "a school full of kids" on Facebook.
A Twitter user also was arrested in the Netherlands in April after tweeting what she claimed was a joke bomb threat to American Airlines.
"There is a reason why they want to do this," Eckersley said. "There have been regular, tragically documented instances where a human being whose crime is being too funny winds up with a pile of agents pointing guns at them and arresting them because they made a joke."