On April 1, the Department of the Treasury's blog touted improvements to USAspending.gov -- a Web site that helps the public figure out where their tax dollars are going. But some thought the refresh was a cruel April Fool's joke, lamenting a "clunky" design and reduced search options.

And now a bipartisan group of senators wants answers.

"Although the redesign does include some improvements, we have concerns that changes to the site's functionality have limited its usefulness to the Congress at the Public," reads a letter to Treasury Secretary Jacob Lew, sent from a group of 11 senators led by Homeland Security and Government Affairs Committee Chairman Ron Johnson (R-Wis.) Thursday night.

Among their chief complaints is that the advanced search function of the new site removed options available in the previous version, such as searching by keyword or for parent companies.

"The Treasury Department needs to answer some basic questions about this update," Johnson told the Post in an e-mailed statement. "Why did Treasury decide to alter the search capabilities in this way? Did anyone consider a beta version to test the update? Most of all, what is the department doing to correct the problems and bring the site back to an acceptable level of function?"

The idea behind USAspending.gov dates back to a 2006 transparency bill. The Department of the Treasury's Bureau of the Fiscal Service​ took over responsibility for the site in January 2014. A Treasury spokesperson said the agency has received the letter and will respond to the senators.

The contractor responsible for the site went bankrupt last year and the government bought back the Web site and underlying data system in October. A major focus of the refresh that followed this spring was making the site more like Recovery.gov -- a move that focused on appealing to a broader user base, but left some open data advocates frustrated by reduced features.

USAspending.gov responded to the initial backlash about the redesign by opening a development forum on popular coding site GitHub where the public could  report bugs and suggest new features -- as well as keep track of its progress on implementing them.

According an update on the site, the agency was still working on adding back keyword search functionality as of April 15. A Treasury official who requested anonymity because he was not authorized to comment on the matter said it expects the feature to return next week.