diff --git a/src/cmd/linuxkit/spec/cache.go b/src/cmd/linuxkit/spec/cache.go
index 2a91112ca..08c23b017 100644
--- a/src/cmd/linuxkit/spec/cache.go
+++ b/src/cmd/linuxkit/spec/cache.go
@@ -4,16 +4,30 @@ import (
 	"io"
 
 	"github.com/containerd/containerd/reference"
-	"github.com/google/go-containerregistry/pkg/v1"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
 )
 
 // CacheProvider interface for a provide of a cache.
 type CacheProvider interface {
+	// FindDescriptor get the first descriptor pointed to by the image name
 	FindDescriptor(name string) (*v1.Descriptor, error)
+	// ImagePull takes an image name and pulls it from a registry to the cache. It should be
+	// efficient and only write missing blobs, based on their content hash. If the ref already
+	// exists in the cache, it should not pull anything, unless alwaysPull is set to true.
 	ImagePull(ref *reference.Spec, trustedRef, architecture string, alwaysPull bool) (ImageSource, error)
+	// IndexWrite takes an image name and creates an index for the descriptors to which it points.
+	// Cache implementation determines whether it should pull missing blobs from a remote registry.
+	// If the provided reference already exists and it is an index, updates the manifests in the
+	// existing index.
 	IndexWrite(ref *reference.Spec, descriptors ...v1.Descriptor) (ImageSource, error)
+	// ImageLoad takes an OCI format image tar stream in the io.Reader and writes it to the cache. It should be
+	// efficient and only write missing blobs, based on their content hash.
 	ImageLoad(ref *reference.Spec, architecture string, r io.Reader) (ImageSource, error)
+	// DescriptorWrite writes a descriptor to the cache index; it validates that it has a name
+	// and replaces any existing one
 	DescriptorWrite(ref *reference.Spec, descriptors v1.Descriptor) (ImageSource, error)
+	// Push push an image along with a multi-arch index from local cache to remote registry.
 	Push(name string) error
+	// NewSource return an ImageSource for a specific ref and architecture in the cache.
 	NewSource(ref *reference.Spec, architecture string, descriptor *v1.Descriptor) ImageSource
 }