diff --git a/content/content.go b/content/content.go
index 05fd4aeb..edcc7a97 100644
--- a/content/content.go
--- b/content/content.go
@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
 // ReaderAt extends the standard io.ReaderAt interface with reporting of Size and io.Closer
@@ -17,12 +18,19 @@ type ReaderAt interface {
 
 // Provider provides a reader interface for specific content
 type Provider interface {
-	ReaderAt(ctx context.Context, dgst digest.Digest) (ReaderAt, error)
+	// ReaderAt only requires desc.Digest to be provided.
+	// Other fields in the descriptor may be used internally for resolving
+	// the location of the actual data.
+	ReaderAt(ctx context.Context, desc ocispec.Descriptor) (ReaderAt, error)
 }
 
 // Ingester writes content
 type Ingester interface {
-	Writer(ctx context.Context, ref string, size int64, expected digest.Digest) (Writer, error)
+	// Writer may optionally use the descriptor internally for resolving
+	// the location of the actual data.
+	// If desc is set but the data size is unknown, desc.Size should be set
+	// to 0. Some implementation also accepts negative values.
+	Writer(ctx context.Context, ref string, desc *ocispec.Descriptor) (Writer, error)
 }
 
 // Info holds content specific information