The phrase "decided together with" is grammatically correct and can be used in written English.
Example sentence: The project's goals were decided together with the team during a brainstorming session.
I've decided together with my husband, doctors and coaches to skip tomorrow's downhill training run.
He continued: "I am now making this a group matter and I have decided together with Picturehouse management to put an end to the consultation process".
"In that context, we explored a wide range of promotional options for the new Coldplay album and ultimately decided, together with management, that Coldplay and its fans would best be served with the full album on both free and premium this Friday".
"The Sydney Roosters wish to advise that following consultation with the club's coaching and welfare staff, it has been decided together with Shaun Kenny-Dowall, that he will not be playing this afternoon," a club statement read before kick-off on Sunday.
Uber at the time decided together with its board that it was resulting in "sustainably high losses," per a Wall Street Journal report.
The organisers decided together with the cyclists to exclude the final kilometre from the race, and make the control post in Ville-d'Avray the end of the race.
What we are doing today is more [a] type of contract where the local authorities is directly deciding together with us on a daily basis; which is a little different from the past where people wanted us to take care of the problem and not looking into how it would be done.
In general, VC's give advice on most aspects of the business and decide together with the management important issues relating to strategic and financial topics.
"The specific details of constitutional reform are for the governments of China and Hong Kong to decide together with the people of Hong Kong".
