Aggregate using project and divide issue

I am trying to figure out how to calculate a golf leaderboard using javascript and aggregate, but am having some issues.

Here is what I am trying to do:

const pipeline = [
  { match: { oomId: oomId, holes: 0 } },
  { group: { 
    objectId: '$userId',
    played: { $sum: 1 },
    puts: {$sum: '$puts'},
    gir: {$sum: '$gir'},
    girHcp: {$sum: '$girHcp'},
    hits: {$sum: '$hit'},
    holesHit: {$sum: '$holesToHit'},
    points: {$sum: '$points'},
    strokes: {$sum: '$strokes'}
  } },
  { project:{ 
      puts: {$divide: {'$puts', '$played'}},
      gir: {$divide: {'$gir', '$played'}},
      girHcp: {$divide: {'$girHcp', '$played'}}
  }}
];

I get this error: Unexpected string

I might be looking at this the wrong way, but not sure how though… Hoping for help 🙂