irb

>> u = User.first
=> …
>> p = u.projects.first
=> …
>> p.name                             # Read from embedded doc
=> "MongoMapper"
>> p.description
=> "A Ruby Object Mapper for Mongo"   # loads lazy attribute

items.json

{
  "name": "Brandon"
  "projects": [
    {"id": ObjectID(…), "name":"MongoMapper"}
  ]
}

models.rb

class User
  include MongoMapper::Document
  key :name
  many :projects, :embed => :name
end

class Project
  include MongoMapper::Document
  key :name
  key :description
end