Context.scala

import cats.implicits._
import cats.{ Applicative, Monad }

// Операции над контекстом

trait ContextWriter[F[_]] {
  def put(key: String, value: String): F[Unit]
}


// Сервисы


class ServiceA[F[_]: Monad](context: ContextWriter[F]) {
  def someSimpleOperation: Int = 1
 
  def someLongOperation: F[Int] = 
    someSimpleOperation
    .pure[F]
    .flatMap { res =>
      context.put("ServiceA.step1", res.toString)
        .as(res * Random.nextInt(10))
    }
    .flatMap { res =>
      context.put("ServiceA.step2", res.toString)
        .as(res - Random.nextInt(5))
    }
}

class ServiceB[F[_]: Monad](serviceA: ServiceA[F], context: ContextWriter[F]) {
  def someOperationWithoutServiceA: Int = 1
 
  def someOperationWithServiceA: F[Boolean] =
    serviceA.someLongOperation.flatMap {
      case res if res % 2 == 0 =>
        context.put("ServiceB.res", "even").as(true)
      case res =>
        context.put("ServiceB.res", "odd").as(false)
    }
}

// Бойлерплейт

type Context = Map[String, String]

class WriterTContextWriter[F[_]: Applicative] extends ContextWriter[WriterT[F, Context, ?]] {
  def put(key: String, value: String): WriterT[F, Context, Unit] = 
    WriterT.tell(Map(key, value))
}

// Вайринг

val contextWriter = new WriterTContextWriter[Future]

val serviceA: ServiceA[WriterT[Future, Context, ?]] = new ServiceA(contextWriter)

val serviceB: ServiceB[WriterT[Future, Context, ?]] = new ServiceB(serviceA, contextWriter)

// Результат

val result: Future[(Context, Boolean)] = serviceB.someOperationWithServiceA.run

result.onComplete {
  case Success((context, result)) =>    
}