Williams, 2008 RBS 6 Nations player of the tournament, scored two brilliant tries as Ospreys crushed semi-final opponents Saracens 30-3 at the Millennium Stadium.
It followed his crucial score when Wales clinched the Grand Slam by beating France in Cardiff seven days ago.
Jones said: "Shane is world-class. Shaun Edwards (Wales defence coach) calls him a predator, which is a perfect description.
"When Shane gets just half-a-chance, he jumps on it."
Jones, Williams and several of their fellow Grand Slam stars made a victorious Millennium Stadium return as the Ospreys booked their second successive EDF final appearance against English heavyweights Leicester.
But they had to work hard before subduing Saracens in a dress rehearsal for next month's Heineken Cup quarter-final clash between these teams at Vicarage Road.
Man-of-the-match Gavin Henson scored the game's critical try on 50 minutes, before replacement back-row forward Filo Tiatia and Williams killed Saracens off.
Fly-half James Hook added two penalties and two conversions, booking a Twickenham appointment with the Tigers on April 12 and an opportunity to avenge last season's 41-35 defeat.
Ospreys coach Lyn Jones added: "We wanted to gel the boys back in after the 6 Nations campaign, and that was a success.
"We need to push on to the next step now. We lost to Leicester by the narrowest of margins last season, and we have grown from that."
Ryan Jones added: "You have very few opportunities to win silverware in your club colours, and we have really grown as a group of individuals.
"It was hugely disappointing to lose to Leicester 12 months ago. But we have come a long way through the experiences we've had, and I am extremely confident in this group of individuals."
Saracens rugby director Alan Gaffney had no complaints about the Ospreys' emphatic success, with his team restricted to a solitary Glen Jackson penalty.
Gaffney said: "We didn't need luck - we needed about five extra players on the pitch.
"They are a classy team, and we've not experienced such a hammering since I have been at Saracens.
"This will be a huge learning curve for us. Ospreys' pressure was very good, and it put us under the hammer.
"We have got to do a bit of homework, but we believe we can turn it around (in the Heineken Cup). We wouldn't be in the competition otherwise."
Saracens scrum-half Neil de Kock and lock Chris Jack both failed to last the distance, with Gaffney confirming former All Blacks star Jack had gone to hospital for an x-ray on his hand.