Fremantle are reportedly keen to lure the 21-year-old West Australian product back to his home state when his existing deal runs out at the end of next year.
But Harley is adamant McDonald will be at the Swans for years to come, having played 44 games for the club since being recruited with pick No.4 in the 2020 draft.
"To use a term from another sport, he's our talisman and he was pick four for us and a cornerstone of our future," Harley told SEN on Thursday.
"Absolutely no doubt about that.
"We value him enormously and I know the type of young man that Logan is; he really values his role in the club and what it looks like going forward.
"He's contracted for next year. I'm sure there will be continued discussions about what his long-term future looks like.
"I think he's going to be thrilling the fans at the SCG for a long time."
The Swans have McDonald, Joel Amartey and Hayden McLean as key forwards still on their books following Lance Franklin's retirement.
Harley declared Sydney's intentions with McDonald after list boss Kinnear Beatson revealed the club "had a crack" at luring fellow key forward Aaron Naughton from the Western Bulldogs.
They were unsuccessful with Naughton signing a massive eight-year extension that ties him to the Dogs until 2032.
Beatson also revealed Taylor Adams' camp initiated the experienced midfielder's bombshell trade from Collingwood.
Adams surprised the Magpies when he requested a move in the days after their premiership.
The 30-year-old is set to get his wish of more midfield time at the Swans, having spent stints at half-forward with Collingwood this year following the arrival of on-baller Tom Mitchell.
Adams will reunite with former Magpies teammate and fellow trade recruit Brodie Grundy at Sydney after the ruckman's move from Melbourne.
Fellow former Demon James Jordon and ex-Fremantle defender Joel Hamling have also joined the Swans - both as free agents - in a productive off-season recruiting drive.
Meanwhile, prospective No.1 draft pick Harley Reid has again attempted to quash ongoing speculation he doesn't want to play for West Coast.
The 18-year-old Victorian midfielder's playing future remains unclear ahead of the national draft on November 20.
The Eagles hold the top selection but North Melbourne are eager to get their hands on the prized pick during the trade period.
Hawthorn and Melbourne are also in the mix.
Reid, from Tongala in Victoria's Goulburn Valley region, laughed off the latest report that he doesn't want to move to Perth when he was quizzed about it during a radio interview on Thursday.
"It kind of rolled me," Reid told SEN WA.
"To all the West Coast people listening, I don't know how many times I have to say it or how much clearer I can be, but I'm happy to go to the Eagles.
"I'm just super grateful to be in the position I am.
"Everything over there seems like it's a great opportunity and good experience obviously with what Perth has to bring."
