diff --git a/src/main/resources/generate.aqua b/src/main/resources/generate.aqua
new file mode 100644
index 00000000..15c6abff
--- /dev/null
+++ b/src/main/resources/generate.aqua
@@ -0,0 +1,8 @@
+service Local("local"):
+    gt: u32, u32 -> bool
+    onIn: string -> ()
+
+func tryGen(in1: u32, in2: string) -> bool:
+    on in2:
+        Local.onIn(in2)
+    Local.gt(in1, 25)
\ No newline at end of file
diff --git a/src/main/scala/aqua/Compiler.scala b/src/main/scala/aqua/Compiler.scala
index 2574820f..996e2b85 100644
--- a/src/main/scala/aqua/Compiler.scala
+++ b/src/main/scala/aqua/Compiler.scala
@@ -23,9 +23,11 @@ import aqua.parser.lexer.Token
 import cats.arrow.FunctionK
 import cats.data.Validated.{Invalid, Valid}
 import cats.data.{EitherK, NonEmptyList, State, ValidatedNel}
-import cats.{Comonad, Eval}
+import cats.Eval
 import cats.free.Free
 import cats.syntax.flatMap._
+import cats.syntax.apply._
+import cats.syntax.semigroup._
 import monocle.Lens
 import monocle.macros.GenLens
 
@@ -52,7 +54,7 @@ object Compiler {
       case expr: OnExpr[F] => expr.program[G]
       case expr: ParExpr[F] => expr.program[G]
       case expr: ServiceExpr[F] => expr.program[G]
-      case _: RootExpr[F] => Free.pure[G, Gen](Gen("Root expr"))
+      case expr: RootExpr[F] => expr.program[G]
     }
 
   def folder[F[_], G[_]](implicit
@@ -64,8 +66,9 @@ object Compiler {
     case (expr, inners) =>
       Eval later exprToProg[F, G](expr)
         .apply(
-          // TODO: instead of >>, do >>= and merge Gens
-          inners.foldLeft(Free.pure[G, Gen](Gen("Folder begin")))(_ >> _)
+          inners
+            .reduceLeftOption[Free[G, Gen]]((a, b) => (a, b).mapN(_ |+| _))
+            .getOrElse(Free.pure(Gen.noop))
         )
   }
 
diff --git a/src/main/scala/aqua/Main.scala b/src/main/scala/aqua/Main.scala
index 052e267e..231aeae8 100644
--- a/src/main/scala/aqua/Main.scala
+++ b/src/main/scala/aqua/Main.scala
@@ -19,7 +19,7 @@ object Main extends IOApp.Simple {
             println(Console.RED + s"Aqua script errored, total ${errs.length} problems found" + Console.RESET)
         }
 
-      val script = Source.fromResource("typecheck.aqua").mkString
+      val script = Source.fromResource("generate.aqua").mkString
       process(script)
 
     }
diff --git a/src/main/scala/aqua/ast/Gen.scala b/src/main/scala/aqua/ast/Gen.scala
index 7157fe58..4a2db0ea 100644
--- a/src/main/scala/aqua/ast/Gen.scala
+++ b/src/main/scala/aqua/ast/Gen.scala
@@ -1,13 +1,21 @@
 package aqua.ast
 
 import aqua.ast.algebra.types.ArrowType
+import cats.Semigroup
 import cats.free.Free
 
-case class Gen(log: String) {
+case class Gen(log: String, children: List[Gen] = Nil) {
   def lift[F[_]]: Free[F, Gen] = Free.pure(this)
 }
 
 object Gen {
+
+  implicit object GenSemigroup extends Semigroup[Gen] {
+
+    override def combine(x: Gen, y: Gen): Gen =
+      x.copy(children = y :: x.children)
+  }
+
   def noop = new Gen("noop")
 
   case class Arrow(`type`: ArrowType, gen: Gen)
diff --git a/src/main/scala/aqua/ast/Prog.scala b/src/main/scala/aqua/ast/Prog.scala
index 98de6835..33311764 100644
--- a/src/main/scala/aqua/ast/Prog.scala
+++ b/src/main/scala/aqua/ast/Prog.scala
@@ -31,4 +31,6 @@ object Prog {
   def around[Alg[_], R, A](before: Free[Alg, R], after: (R, A) => Free[Alg, A]): Prog[Alg, A] =
     RunAround(before, after)
 
+  def noop[Alg[_], A]: Prog[Alg, A] =
+    RunAround(Free.pure(()), (_: Unit, a: A) => Free.pure(a))
 }
diff --git a/src/main/scala/aqua/ast/algebra/abilities/AbilitiesInterpreter.scala b/src/main/scala/aqua/ast/algebra/abilities/AbilitiesInterpreter.scala
index c6b42091..674e3066 100644
--- a/src/main/scala/aqua/ast/algebra/abilities/AbilitiesInterpreter.scala
+++ b/src/main/scala/aqua/ast/algebra/abilities/AbilitiesInterpreter.scala
@@ -8,6 +8,7 @@ import cats.~>
 import cats.syntax.functor._
 import monocle.Lens
 import monocle.macros.GenLens
+import monocle.macros.syntax.all._
 
 class AbilitiesInterpreter[F[_], X](implicit lens: Lens[X, AbilitiesState[F]], error: ReportError[F, X])
     extends StackInterpreter[F, X, AbilitiesState[F], AbilityStackFrame[F]](GenLens[AbilitiesState[F]](_.stack))
@@ -35,6 +36,8 @@ class AbilitiesInterpreter[F[_], X](implicit lens: Lens[X, AbilitiesState[F]], e
       case ga: GetArrow[F] =>
         getService(ga.name.value).flatMap {
           case Some(arrows) =>
+            // TODO: must be resolved
+
             arrows(ga.arrow.value)
               .fold(
                 report(
@@ -50,7 +53,7 @@ class AbilitiesInterpreter[F[_], X](implicit lens: Lens[X, AbilitiesState[F]], e
         getService(s.name.value).flatMap {
           case Some(_) =>
             mapStackHead(
-              report(s.name, "Trying to set service ID while out of the scope").as(false)
+              modify(_.focus(_.rootServiceIds).index(s.name.value).replace(s.id)).as(true)
             )(h => h.copy(serviceIds = h.serviceIds.updated(s.name.value, s.id)) -> true)
 
           case None =>
@@ -79,7 +82,8 @@ class AbilitiesInterpreter[F[_], X](implicit lens: Lens[X, AbilitiesState[F]], e
 
 case class AbilitiesState[F[_]](
   stack: List[AbilityStackFrame[F]] = Nil,
-  services: Map[String, NonEmptyMap[String, ArrowType]] = Map.empty
+  services: Map[String, NonEmptyMap[String, ArrowType]] = Map.empty,
+  rootServiceIds: Map[String, Value[F]] = Map.empty[String, Value[F]]
 ) {
 
   def purgeArrows: Option[(NonEmptyList[(Name[F], ArrowType)], AbilitiesState[F])] =
diff --git a/src/main/scala/aqua/ast/expr/AbilityIdExpr.scala b/src/main/scala/aqua/ast/expr/AbilityIdExpr.scala
index 7d4056e6..465a26d3 100644
--- a/src/main/scala/aqua/ast/expr/AbilityIdExpr.scala
+++ b/src/main/scala/aqua/ast/expr/AbilityIdExpr.scala
@@ -14,7 +14,7 @@ import cats.syntax.functor._
 case class AbilityIdExpr[F[_]](ability: Ability[F], id: Value[F]) extends Expr[F] {
 
   def program[Alg[_]](implicit A: AbilitiesAlgebra[F, Alg], V: ValuesAlgebra[F, Alg]): Prog[Alg, Gen] =
-    V.ensureIsString(id) >> A.setServiceId(ability, id) as Gen.noop
+    V.ensureIsString(id) >> A.setServiceId(ability, id) as Gen(s"Ability id is set for ${ability.value}")
 
 }
 
diff --git a/src/main/scala/aqua/ast/expr/AliasExpr.scala b/src/main/scala/aqua/ast/expr/AliasExpr.scala
index 111cafe9..fb3aed53 100644
--- a/src/main/scala/aqua/ast/expr/AliasExpr.scala
+++ b/src/main/scala/aqua/ast/expr/AliasExpr.scala
@@ -14,8 +14,8 @@ case class AliasExpr[F[_]](name: CustomTypeToken[F], target: TypeToken[F]) exten
 
   def program[Alg[_]](implicit T: TypesAlgebra[F, Alg]): Prog[Alg, Gen] =
     T.resolveType(target).flatMap {
-      case Some(t) => T.defineAlias(name, t).as(Gen.noop)
-      case None => Free.pure(Gen.noop)
+      case Some(t) => T.defineAlias(name, t) as Gen(s"Alias ${name.value} defined")
+      case None => Free.pure(Gen(s"Alias ${name.value} can't be defined"))
     }
 
 }
diff --git a/src/main/scala/aqua/ast/expr/ArrowTypeExpr.scala b/src/main/scala/aqua/ast/expr/ArrowTypeExpr.scala
index 5e842500..c5413b33 100644
--- a/src/main/scala/aqua/ast/expr/ArrowTypeExpr.scala
+++ b/src/main/scala/aqua/ast/expr/ArrowTypeExpr.scala
@@ -15,8 +15,8 @@ case class ArrowTypeExpr[F[_]](name: Name[F], `type`: ArrowTypeToken[F]) extends
 
   def program[Alg[_]](implicit T: TypesAlgebra[F, Alg], A: AbilitiesAlgebra[F, Alg]): Prog[Alg, Gen] =
     T.resolveArrowDef(`type`).flatMap {
-      case Some(t) => A.defineArrow(name, t).as(Gen.noop)
-      case None => Free.pure(Gen.noop)
+      case Some(t) => A.defineArrow(name, t) as Gen(s"Arrow $name defined")
+      case None => Free.pure(Gen(s"Arrow $name can't be defined"))
     }
 
 }
diff --git a/src/main/scala/aqua/ast/expr/CoalgebraExpr.scala b/src/main/scala/aqua/ast/expr/CoalgebraExpr.scala
index ddc9356b..6af7692d 100644
--- a/src/main/scala/aqua/ast/expr/CoalgebraExpr.scala
+++ b/src/main/scala/aqua/ast/expr/CoalgebraExpr.scala
@@ -38,7 +38,8 @@ case class CoalgebraExpr[F[_]](
                 Free.pure[Alg, Boolean](false)
               )(resType => N.define(exportVar, resType))
             // TODO: if it's a service, get service id, etc
-            ) as Gen("Coalgebra expression")
+            ) as Gen(s"(call peer (${ability.map(_.value).getOrElse("func")} ${funcName.value}) [${args
+            .mkString(", ")}]${variable.map(" " + _).getOrElse("")})")
         case None =>
           Free.pure(Gen("Coalgebra expression errored"))
       }
diff --git a/src/main/scala/aqua/ast/expr/DataStructExpr.scala b/src/main/scala/aqua/ast/expr/DataStructExpr.scala
index 843d741b..16fed2dd 100644
--- a/src/main/scala/aqua/ast/expr/DataStructExpr.scala
+++ b/src/main/scala/aqua/ast/expr/DataStructExpr.scala
@@ -20,8 +20,8 @@ case class DataStructExpr[F[_]](name: CustomTypeToken[F]) extends Expr[F] {
     Prog after T
       .purgeFields(name)
       .flatMap {
-        case Some(fields) => T.defineDataType(name, fields).as(Gen("Data struct created"))
-        case None => Free.pure(Gen.noop)
+        case Some(fields) => T.defineDataType(name, fields) as Gen(s"Data struct ${name.value} created")
+        case None => Free.pure(Gen(s"Data struct ${name.value} can't be created"))
       }
 
 }
diff --git a/src/main/scala/aqua/ast/expr/FieldTypeExpr.scala b/src/main/scala/aqua/ast/expr/FieldTypeExpr.scala
index e6dc03dd..b0fd93e1 100644
--- a/src/main/scala/aqua/ast/expr/FieldTypeExpr.scala
+++ b/src/main/scala/aqua/ast/expr/FieldTypeExpr.scala
@@ -14,8 +14,8 @@ case class FieldTypeExpr[F[_]](name: Name[F], `type`: DataTypeToken[F]) extends
 
   def program[Alg[_]](implicit T: TypesAlgebra[F, Alg]): Prog[Alg, Gen] =
     T.resolveType(`type`).flatMap {
-      case Some(t) => T.defineField(name, t).as(Gen.noop)
-      case None => Free.pure(Gen.noop)
+      case Some(t) => T.defineField(name, t) as Gen(s"Field ${name.value} defined")
+      case None => Free.pure(Gen(s"Field ${name.value} can't be defined"))
     }
 
 }
diff --git a/src/main/scala/aqua/ast/expr/FuncExpr.scala b/src/main/scala/aqua/ast/expr/FuncExpr.scala
index 57a5425d..676a2a4c 100644
--- a/src/main/scala/aqua/ast/expr/FuncExpr.scala
+++ b/src/main/scala/aqua/ast/expr/FuncExpr.scala
@@ -53,7 +53,8 @@ case class FuncExpr[F[_]](name: Name[F], args: List[Arg[F]], ret: Option[DataTyp
       (funcArrow: ArrowType, bodyGen: Gen) =>
         // Erase arguments and internal variables
         A.endScope() >> N.endScope() >> N.define(name, funcArrow, isRoot = true) as Gen(
-          "Function defined, wrap + " + bodyGen
+          s"func ${name.value}:",
+          bodyGen :: Nil
         )
     )
 
diff --git a/src/main/scala/aqua/ast/expr/OnExpr.scala b/src/main/scala/aqua/ast/expr/OnExpr.scala
index 26d7b12a..40bbbd46 100644
--- a/src/main/scala/aqua/ast/expr/OnExpr.scala
+++ b/src/main/scala/aqua/ast/expr/OnExpr.scala
@@ -21,7 +21,7 @@ case class OnExpr[F[_]](peerId: Value[F]) extends Expr[F] {
   ): Prog[Alg, Gen] =
     Prog.around(
       V.ensureIsString(peerId) >> P.onPeerId(peerId) >> A.beginScope(peerId),
-      (_: Unit, ops: Gen) => A.endScope() >> P.erasePeerId() as Gen("OnScope finished for" + ops)
+      (_: Unit, ops: Gen) => A.endScope() >> P.erasePeerId() as ops
     )
 
 }
diff --git a/src/main/scala/aqua/ast/expr/RootExpr.scala b/src/main/scala/aqua/ast/expr/RootExpr.scala
index 7bc1c294..e76c56fa 100644
--- a/src/main/scala/aqua/ast/expr/RootExpr.scala
+++ b/src/main/scala/aqua/ast/expr/RootExpr.scala
@@ -1,7 +1,11 @@
 package aqua.ast.expr
 
-import aqua.ast.Expr
+import aqua.ast.{Expr, Gen, Prog}
 
-case class RootExpr[F[_]]() extends Expr[F] {}
+case class RootExpr[F[_]]() extends Expr[F] {
+
+  def program[Alg[_]]: Prog[Alg, Gen] =
+    Prog.noop
+}
 
 object RootExpr
diff --git a/src/main/scala/aqua/ast/expr/ServiceExpr.scala b/src/main/scala/aqua/ast/expr/ServiceExpr.scala
index df7ec2c2..83a1adcf 100644
--- a/src/main/scala/aqua/ast/expr/ServiceExpr.scala
+++ b/src/main/scala/aqua/ast/expr/ServiceExpr.scala
@@ -29,11 +29,11 @@ case class ServiceExpr[F[_]](name: Ability[F], id: Option[Value[F]]) extends Exp
         (A.purgeArrows(name) <* A.endScope()).flatMap {
           case Some(nel) =>
             A.defineService(name, nel.map(kv => kv._1.value -> kv._2).toNem) >>
-              id.fold(Free.pure[Alg, Gen](Gen.noop))(idV =>
-                V.ensureIsString(idV) >> A.setServiceId(name, idV) as Gen.noop
+              id.fold(Free.pure[Alg, Gen](Gen(s"Service ${name.value} created")))(idV =>
+                V.ensureIsString(idV) >> A.setServiceId(name, idV) as Gen(s"Service ${name.value} created with ID")
               )
           case None =>
-            Gen.noop.lift
+            Gen(s"Cannot create service ${name.value}").lift
 
         }
     )