diff --git a/pkg/policy/encode.go b/pkg/policy/encode.go
index a7d3ef0..e003445 100644
--- a/pkg/policy/encode.go
+++ b/pkg/policy/encode.go
@@ -8,6 +8,7 @@ import (
 	"github.com/nspcc-dev/neofs-api-go/pkg/netmap"
 )
 
+// Encode parses data of PlacementPolicy to a string.
 func Encode(p *netmap.PlacementPolicy) []string {
 	if p == nil {
 		return nil
diff --git a/pkg/policy/json.go b/pkg/policy/json.go
index a0b474f..3169bdb 100644
--- a/pkg/policy/json.go
+++ b/pkg/policy/json.go
@@ -54,7 +54,7 @@ func ToJSON(np *netmap.PlacementPolicy) ([]byte, error) {
 	return json.Marshal(p)
 }
 
-// ToJSON creates placement policy from JSON.
+// FromJSON creates placement policy from JSON.
 func FromJSON(data []byte) (*netmap.PlacementPolicy, error) {
 	p := new(placement)
 	if err := json.Unmarshal(data, p); err != nil {
diff --git a/pkg/policy/query.go b/pkg/policy/query.go
index 4904279..1b6447e 100644
--- a/pkg/policy/query.go
+++ b/pkg/policy/query.go
@@ -9,10 +9,15 @@ import (
 )
 
 var (
-	ErrInvalidNumber   = errors.New("policy: expected positive integer")
-	ErrUnknownClause   = errors.New("policy: unknown clause")
-	ErrUnknownOp       = errors.New("policy: unknown operation")
-	ErrUnknownFilter   = errors.New("policy: filter not found")
+	// ErrInvalidNumber is returned when a value of SELECT is 0.
+	ErrInvalidNumber = errors.New("policy: expected positive integer")
+	// ErrUnknownClause is returned when a statement(clause) in a query is unknown.
+	ErrUnknownClause = errors.New("policy: unknown clause")
+	// ErrUnknownOp is returned when an operation in a query is unknown.
+	ErrUnknownOp = errors.New("policy: unknown operation")
+	// ErrUnknownFilter is returned when a value of FROM in a query is unknown.
+	ErrUnknownFilter = errors.New("policy: filter not found")
+	// ErrUnknownSelector is returned when a value of IN is unknown.
 	ErrUnknownSelector = errors.New("policy: selector not found")
 )
 
diff --git a/pkg/policy/query_test.go b/pkg/policy/query_test.go
index b7c4cc7..ebe2be2 100644
--- a/pkg/policy/query_test.go
+++ b/pkg/policy/query_test.go
@@ -62,7 +62,6 @@ func TestFromSelectNoAttribute(t *testing.T) {
 		r, err := Parse(q)
 		require.NoError(t, err)
 		require.EqualValues(t, expected, r)
-
 	})
 
 	t.Run("with filter", func(t *testing.T) {
@@ -232,7 +231,6 @@ func TestValidation(t *testing.T) {
 		_, err := Parse(q)
 		require.True(t, errors.Is(err, ErrInvalidNumber), "got: %v", err)
 	})
-
 }
 
 func TestFilterStringSymbols(t *testing.T) {