diff --git a/client/client.go b/client/client.go
index ce0c9ee..aa873e5 100644
--- a/client/client.go
+++ b/client/client.go
@@ -74,6 +74,10 @@ func (c *Client) Init(prm PrmInit) {
 // One-time method call during application start-up stage (after Init ) is expected.
 // Calling multiple times leads to undefined behavior.
 //
+// Return client errors:
+//   - [ErrMissingServer]
+//   - [ErrNonPositiveTimeout]
+//
 // See also Init / Close.
 func (c *Client) Dial(prm PrmDial) error {
 	if prm.endpoint == "" {
diff --git a/client/errors.go b/client/errors.go
index bd9d7e2..da55c52 100644
--- a/client/errors.go
+++ b/client/errors.go
@@ -6,23 +6,38 @@ import (
 )
 
 var (
-	ErrMissingServer      = errors.New("server address is unset or empty")
+	// ErrMissingServer is returned when server endpoint is empty in parameters.
+	ErrMissingServer = errors.New("server address is unset or empty")
+	// ErrNonPositiveTimeout is returned when any timeout is below zero in parameters.
 	ErrNonPositiveTimeout = errors.New("non-positive timeout")
 
-	ErrMissingContainer     = errors.New("missing container")
-	ErrMissingObject        = errors.New("missing object")
-	ErrMissingAccount       = errors.New("missing account")
-	ErrMissingEACL          = errors.New("missing eACL table")
+	// ErrMissingContainer is returned when container is not provided.
+	ErrMissingContainer = errors.New("missing container")
+	// ErrMissingObject is returned when object is not provided.
+	ErrMissingObject = errors.New("missing object")
+	// ErrMissingAccount is returned when account/owner is not provided.
+	ErrMissingAccount = errors.New("missing account")
+	// ErrMissingEACL is returned when eACL table is not provided.
+	ErrMissingEACL = errors.New("missing eACL table")
+	// ErrMissingEACLContainer is returned when container info is not provided in eACL table.
 	ErrMissingEACLContainer = errors.New("missing container in eACL table")
+	// ErrMissingAnnouncements is returned when announcements are not provided.
 	ErrMissingAnnouncements = errors.New("missing announcements")
-	ErrZeroRangeLength      = errors.New("zero range length")
-	ErrMissingRanges        = errors.New("missing ranges")
-	ErrZeroEpoch            = errors.New("zero epoch")
-	ErrMissingTrusts        = errors.New("missing trusts")
-	ErrMissingTrust         = errors.New("missing trust")
+	// ErrZeroRangeLength is returned when range parameter has zero length.
+	ErrZeroRangeLength = errors.New("zero range length")
+	// ErrMissingRanges is returned when empty ranges list is provided.
+	ErrMissingRanges = errors.New("missing ranges")
+	// ErrZeroEpoch is returned when zero epoch is provided.
+	ErrZeroEpoch = errors.New("zero epoch")
+	// ErrMissingTrusts is returned when empty slice of trusts is provided.
+	ErrMissingTrusts = errors.New("missing trusts")
+	// ErrMissingTrust is returned when empty trust is not provided.
+	ErrMissingTrust = errors.New("missing trust")
 
+	// ErrUnexpectedReadCall is returned when we already got all data but truing to get more.
 	ErrUnexpectedReadCall = errors.New("unexpected call to `Read`")
 
+	// ErrSign is returned when unable to sign service message.
 	ErrSign SignError
 
 	errMissingResponseField missingResponseFieldErr
@@ -56,22 +71,27 @@ func newErrInvalidResponseField(name string, err error) error {
 	return fmt.Errorf("invalid %s field in the response: %w", name, err)
 }
 
+// SignError wraps another error with reason why sign process was failed.
 type SignError struct {
 	err error
 }
 
+// NewSignError is a constructor for [SignError].
 func NewSignError(err error) SignError {
 	return SignError{err: err}
 }
 
+// Error implements the error interface.
 func (e SignError) Error() string {
 	return fmt.Sprintf("sign: %v", e.err)
 }
 
+// Unwrap implements the error interface.
 func (e SignError) Unwrap() error {
 	return e.err
 }
 
+// Is implements interface for correct checking current error type with [errors.Is].
 func (e SignError) Is(target error) bool {
 	switch target.(type) {
 	default:
diff --git a/client/netmap.go b/client/netmap.go
index 7d955f5..27614c1 100644
--- a/client/netmap.go
+++ b/client/netmap.go
@@ -41,6 +41,8 @@ func (x ResEndpointInfo) NodeInfo() netmap.NodeInfo {
 // Any client's internal or transport errors are returned as `error`,
 // see [apistatus] package for NeoFS-specific error types.
 //
+// Context is required and must not be nil. It is used for network communication.
+//
 // Exactly one return value is non-nil. Server status return is returned in ResEndpointInfo.
 // Reflects all internal errors in second return value (transport problems, response processing, etc.).
 func (c *Client) EndpointInfo(ctx context.Context, prm PrmEndpointInfo) (*ResEndpointInfo, error) {
@@ -122,6 +124,8 @@ func (x ResNetworkInfo) Info() netmap.NetworkInfo {
 // Any client's internal or transport errors are returned as `error`,
 // see [apistatus] package for NeoFS-specific error types.
 //
+// Context is required and must not be nil. It is used for network communication.
+//
 // Exactly one return value is non-nil. Server status return is returned in ResNetworkInfo.
 // Reflects all internal errors in second return value (transport problems, response processing, etc.).
 func (c *Client) NetworkInfo(ctx context.Context, prm PrmNetworkInfo) (*ResNetworkInfo, error) {
diff --git a/client/object_hash.go b/client/object_hash.go
index 734627b..847a801 100644
--- a/client/object_hash.go
+++ b/client/object_hash.go
@@ -157,6 +157,7 @@ func (x ResObjectHash) Checksums() [][]byte {
 // Return errors:
 //   - [ErrMissingContainer]
 //   - [ErrMissingObject]
+//   - [ErrMissingRanges]
 func (c *Client) ObjectHash(ctx context.Context, prm PrmObjectHash) (*ResObjectHash, error) {
 	switch {
 	case prm.addr.GetContainerID() == nil:
diff --git a/user/util.go b/user/util.go
index 3022ff9..c43d3ec 100644
--- a/user/util.go
+++ b/user/util.go
@@ -8,6 +8,7 @@ import (
 	neofscrypto "github.com/nspcc-dev/neofs-sdk-go/crypto"
 )
 
+// ErrOwnerExtract is returned when failed to extract account info from key.
 var ErrOwnerExtract = errors.New("decode owner failed")
 
 // IDFromKey forms the ID using script hash calculated for the given key.