diff --git a/tools/filesystem/blob/bucket.go b/tools/filesystem/blob/bucket.go
index 6d744f5d..23464be3 100644
--- a/tools/filesystem/blob/bucket.go
+++ b/tools/filesystem/blob/bucket.go
@@ -387,11 +387,10 @@ func (b *Bucket) Attributes(ctx context.Context, key string) (_ *Attributes, err
 	}, nil
 }
 
-// Exists returns true if a blob exists at key, false if it does not exist, or
-// an error.
+// Exists returns true if a blob exists at key, false if it does not exist, or an error.
 //
-// It is a shortcut for calling Attributes and checking if it returns an error
-// with code ErrNotFound.
+// It is a shortcut for calling Attributes and checking if it returns
+// an error with code ErrNotFound.
 func (b *Bucket) Exists(ctx context.Context, key string) (bool, error) {
 	_, err := b.Attributes(ctx, key)
 	if err == nil {
@@ -419,11 +418,8 @@ func (b *Bucket) NewReader(ctx context.Context, key string) (*Reader, error) {
 //
 // Note that ctx is used for all reads performed during the lifetime of the reader.
 //
-// If the blob does not exist, NewRangeReader returns an error for which
-// gcerrors.Code will return gcerrors.NotFound. Exists is a lighter-weight way
-// to check for existence.
-//
-// A nil ReaderOptions is treated the same as the zero value.
+// If the blob does not exist, NewRangeReader returns an ErrNotFound.
+// Exists is a lighter-weight wayto check for existence.
 //
 // The caller must call Close on the returned Reader when done reading.
 func (b *Bucket) NewRangeReader(ctx context.Context, key string, offset, length int64) (_ *Reader, err error) {
@@ -656,8 +652,7 @@ func (b *Bucket) NewWriter(ctx context.Context, key string, opts *WriterOptions)
 // Copy the blob stored at srcKey to dstKey.
 // A nil CopyOptions is treated the same as the zero value.
 //
-// If the source blob does not exist, Copy returns an error for which
-// gcerrors.Code will return gcerrors.NotFound.
+// If the source blob does not exist, Copy returns an ErrNotFound.
 //
 // If the destination blob already exists, it is overwritten.
 func (b *Bucket) Copy(ctx context.Context, dstKey, srcKey string) (err error) {
diff --git a/tools/filesystem/blob/driver.go b/tools/filesystem/blob/driver.go
index 7cae2c9b..b8dd727c 100644
--- a/tools/filesystem/blob/driver.go
+++ b/tools/filesystem/blob/driver.go
@@ -40,7 +40,7 @@ type Driver interface {
 	NormalizeError(err error) error
 
 	// Attributes returns attributes for the blob. If the specified object does
-	// not exist, Attributes must return an error for which ErrorCode returns ErrNotFound.
+	// not exist, Attributes must return an ErrNotFound.
 	// The portable type will not modify the returned Attributes.
 	Attributes(ctx context.Context, key string) (*Attributes, error)
 
@@ -50,19 +50,12 @@ type Driver interface {
 	// to recently written or deleted objects. That is to say, there is no
 	// guarantee that an object that's been written will immediately be returned
 	// from ListPaged.
-	// opts is guaranteed to be non-nil.
 	ListPaged(ctx context.Context, opts *ListOptions) (*ListPage, error)
 
 	// NewRangeReader returns a Reader that reads part of an object, reading at
 	// most length bytes starting at the given offset. If length is negative, it
 	// will read until the end of the object. If the specified object does not
-	// exist, NewRangeReader must return an error for which ErrorCode returns ErrNotFound.
-	// opts is guaranteed to be non-nil.
-	//
-	// The returned Reader *may* also implement Downloader if the underlying
-	// implementation can take advantage of that. The Download call is guaranteed
-	// to be the only call to the Reader. For such readers, offset will always
-	// be 0 and length will always be -1.
+	// exist, NewRangeReader must return an ErrNotFound.
 	NewRangeReader(ctx context.Context, key string, offset, length int64) (DriverReader, error)
 
 	// NewTypedWriter returns Writer that writes to an object associated with key.
@@ -87,16 +80,13 @@ type Driver interface {
 
 	// Copy copies the object associated with srcKey to dstKey.
 	//
-	// If the source object does not exist, Copy must return an error for which
-	// ErrorCode returns ErrNotFound.
+	// If the source object does not exist, Copy must return an ErrNotFound.
 	//
 	// If the destination object already exists, it should be overwritten.
-	//
-	// opts is guaranteed to be non-nil.
 	Copy(ctx context.Context, dstKey, srcKey string) error
 
 	// Delete deletes the object associated with key. If the specified object does
-	// not exist, Delete must return an error for which ErrorCode returns ErrNotFound.
+	// not exist, Delete must return an ErrNotFound.
 	Delete(ctx context.Context, key string) error
 
 	// Close cleans up any resources used by the Bucket. Once Close is called,