Here are some usage examples of the library:

```elixir
defmodule MyApp.CreateUser do
  use Ecto.Command, repo: MyApp.Repo

  command "create_user"

  param :name, :string, required: true
  param :email, :string, required: true
  param :age, :integer, default: 18
  param :password, :string, required: true
  param :address do
    param :street, :string, required: true
    param :city, :string, required: true
    param :state, :string, required: true
    param :zip, :string, required: true
  end

  def execute(params) do
    # validate and process the params as needed
    # create the user and return the result
  end
end
```

```elixir
defmodule MyApp.UpdateUser do
  use Ecto.Command, repo: MyApp.Repo

  command "update_user"

  param :id, :integer, required: true
  param :name, :string
  param :email, :string
  param :age, :integer
  param :password, :string
  param :address do
    param :street, :string
    param :city, :string
    param :state, :string
    param :zip, :string
  end

  def execute(params) do
    # validate and process the params as needed
    # update the user and return the result
  end
end
```