Designing Services: Utility Functions on the Service or "Loose" Utility Functions?

interface MyService { foo: string,  doSomeStuff(): T.Effect<....> }

//use it
pipe(....,
  T.flatMap(MyService, s => s.doSomeStuff()),
   ....
)

interface MyService { foo: string }
export const doSomeStuff = () => T.flatMap(MyService, s => pipe(....do the same stuff....))

//use it
pipe(....,
  doSomeStuff(),
   ....
)