diff --git a/cmd/check/main.go b/cmd/check/main.go
index 9c89c97..508fc6b 100644
--- a/cmd/check/main.go
+++ b/cmd/check/main.go
@@ -33,6 +33,10 @@ func main() {
 
 	if req.Version != nil {
 		response = append(response, *req.Version)
+	} else if !req.Source.NoInitialVersion {
+		response = append(response, resource.Version{
+			Version: "mirror",
+		})
 	}
 
 	json.NewEncoder(os.Stdout).Encode(response)
diff --git a/cmd/in/main.go b/cmd/in/main.go
index 7f9df5a..135d78d 100644
--- a/cmd/in/main.go
+++ b/cmd/in/main.go
@@ -12,8 +12,9 @@ import (
 )
 
 type InRequest struct {
-	Source  resource.Source  `json:"source"`
-	Version resource.Version `json:"version"`
+	Source  resource.Source    `json:"source"`
+	Version resource.Version   `json:"version"`
+	Params  resource.GetParams `json:"params"`
 }
 
 type InResponse struct {
@@ -56,7 +57,7 @@ func main() {
 		return
 	}
 
-	if req.Source.FetchImage {
+	if req.Source.MirrorSelf || req.Params.MirrorSelfViaParams {
 		replicateTo(filepath.Join(dest, "rootfs"))
 
 		encTo(filepath.Join(dest, "metadata.json"), ImageMetadata{
diff --git a/types.go b/types.go
index 48f1a15..f15aaae 100644
--- a/types.go
+++ b/types.go
@@ -1,13 +1,23 @@
 package resource
 
 type Source struct {
-	FetchImage bool `json:"fetch_image"`
+	// fetch the resource itself as an image
+	MirrorSelf bool `json:"mirror_self"`
+
+	// don't emit an initial version; useful for testing pipeline triggering
+	NoInitialVersion bool `json:"no_initial_version"`
 }
 
 type Version struct {
 	Version string `json:"version"`
 }
 
+type GetParams struct {
+	// same as configuring MirrorSelf in source, but in params, so that we can
+	// test params are respected in places
+	MirrorSelfViaParams bool `json:"mirror_self_via_params"`
+}
+
 type MetadataField struct {
 	Name  string `json:"name"`
 	Value string `json:"value"`