Williams, also New Zealand's heavyweight boxing champion, left the All Blacks and Waikato Chiefs for a 12-match contract in Japan worth a reported $100,000 per appearance.
"He's just played two absolutely outstanding Tests against Australia and with his profile he will bring an enormous amount of interest," Jones told Reuters.
"To have a regular All Black, and one who's maybe even a little more special, with his background in rugby league and the boxing, come in is tremendous for Japanese rugby."
Williams will sit out Saturday's Top League opener against Ricoh Black Rams after helping world champions New Zealand crush Australia 22-0 to retain the Bledisloe Cup last weekend.
Jones backed the 27-year-old centre to win over sceptics ready to label Williams, who has a history of switching clubs and codes, an extravagance.
"I've only met him a couple of times but he seems like a humble guy and he always puts his body on the line, be it for the Chiefs or the All Blacks," said Jones.
"If Panasonic are willing to pay that sort of money for him to play, good luck to him. I think he'll be good value for money."
Panasonic's next game is on September 9 against NTT Communications Shining Arcs in Sapporo.
Jones, who took over as Japan coach after last year's World Cup, made no secret of the fact that taking the 'Brave Blossoms' to the next level was a work in progress.
"The reality is Japan haven't won a World Cup game for 20 years," said the Australian, who took over the job from former All Black John Kirwan in December.
"The picture's not great but we're trying to maximise Japan's strengths with quick, fit and skilful players. They've always been admired for their inventiveness and courage."
Japan's one World Cup win in 24 matches came against Zimbabwe in 1991.
Kirwan's target of two wins at the World Cup crumbled to dust as they were beaten by hosts New Zealand, France and Tonga before drawing 23-23 with Canada.
"It's about taking the small steps to improve," said Jones.