diff --git a/cmd/actionExecute.go b/cmd/actionExecute.go
index d68633f..4a80139 100644
--- a/cmd/actionExecute.go
+++ b/cmd/actionExecute.go
@@ -1,7 +1,6 @@
 package cmd
 
 import (
-	"encoding/json"
 	"fmt"
 	"log"
 	"time"
@@ -91,21 +90,11 @@ func actionExecute() {
 		log.Fatalf("error: failed to get action: %v", err)
 	}
 
-	itemJson, err := json.Marshal(item)
+	newItem, err := core.ExecuteItemAction(item, actionExecuteSource, argv, time.Minute)
 	if err != nil {
-		log.Fatalf("error: failed to serialize item: %v", err)
+		log.Fatalf("error executing action: %v", err)
 	}
 
-	res, err := core.Execute(actionExecuteSource, argv, nil, string(itemJson), time.Minute)
-	if err != nil {
-		log.Fatalf("error: failed to execute action: %v", err)
-	}
-	if len(res) != 1 {
-		log.Fatalf("error: expected action to produce exactly one item, got %d", len(res))
-	}
-	newItem := res[0]
-	core.BackfillItem(&newItem, &item)
-
 	if actionExecuteDiff {
 		if item.Title != newItem.Title {
 			log.Printf("title: %s => %s", item.Title, newItem.Title)
@@ -128,7 +117,7 @@ func actionExecute() {
 	}
 
 	if actionExecuteDryRun {
-		fmt.Println(formatter(res[0]))
+		fmt.Println(formatter(newItem))
 		return
 	}
 
diff --git a/core/action.go b/core/action.go
index 7582f54..b10151e 100644
--- a/core/action.go
+++ b/core/action.go
@@ -6,6 +6,7 @@ import (
 	"database/sql/driver"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"io"
 	"log"
 	"os"
@@ -206,3 +207,28 @@ func Execute(
 
 	return items, nil
 }
+
+// Execute an action that takes an item as input and returns the item modified.
+func ExecuteItemAction(
+	item Item,
+	action string,
+	argv []string,
+	timeout time.Duration,
+) (Item, error) {
+	itemJson, err := json.Marshal(item)
+	if err != nil {
+		return Item{}, fmt.Errorf("failed to serialize item: %v", err)
+	}
+
+	res, err := Execute(item.Source, argv, nil, string(itemJson), time.Minute)
+	if err != nil {
+		return Item{}, fmt.Errorf("failed to execute %s for %s/%s: %v", action, item.Source, item.Id, err)
+	}
+	if len(res) != 1 {
+		return Item{}, fmt.Errorf("expected action to produce exactly one item, got %d", len(res))
+	}
+	newItem := res[0]
+	BackfillItem(&newItem, &item)
+
+	return newItem, nil
+}
diff --git a/core/source.go b/core/source.go
index 7fb4cb1..37c18b7 100644
--- a/core/source.go
+++ b/core/source.go
@@ -284,20 +284,10 @@ func UpdateWithFetchedItems(db *DB, source string, items []Item) (int, int, erro
 	if err == nil {
 		var updatedNewItems []Item
 		for _, item := range newItems {
-			itemJson, err := json.Marshal(item)
+			updatedItem, err := ExecuteItemAction(item, "on_create", onCreateArgv, time.Minute)
 			if err != nil {
-				log.Fatalf("error: failed to serialize item: %v", err)
+				log.Printf("error: %v", err)
 			}
-			res, err := Execute(source, onCreateArgv, nil, string(itemJson), time.Minute)
-			if err != nil {
-				log.Printf("error: failed to execute on_create for %s/%s: %v", item.Source, item.Id, err)
-				continue
-			}
-			if len(res) != 1 {
-				log.Printf("error: expected on_create for %s/%s to produce exactly one item, got %d", item.Source, item.Id, len(res))
-			}
-			updatedItem := res[0]
-			BackfillItem(&updatedItem, &item)
 			updatedNewItems = append(updatedNewItems, updatedItem)
 		}
 		UpdateItems(db, updatedNewItems)
diff --git a/web/item.go b/web/item.go
index c7347fc..76e3a5d 100644
--- a/web/item.go
+++ b/web/item.go
@@ -1,7 +1,6 @@
 package web
 
 import (
-	"encoding/json"
 	"log"
 	"net/http"
 	"strings"
@@ -62,24 +61,12 @@ func (env *Env) doAction(writer http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	itemJson, err := json.Marshal(item)
+	newItem, err := core.ExecuteItemAction(item, action, argv, time.Minute)
 	if err != nil {
 		http.Error(writer, err.Error(), 500)
 		return
 	}
 
-	res, err := core.Execute(source, argv, nil, string(itemJson), time.Minute)
-	if err != nil {
-		http.Error(writer, err.Error(), 500)
-		return
-	}
-	if len(res) != 1 {
-		http.Error(writer, "not exactly one item", 500)
-		return
-	}
-	newItem := res[0]
-	core.BackfillItem(&newItem, &item)
-
 	if err = core.UpdateItems(env.db, []core.Item{newItem}); err != nil {
 		http.Error(writer, err.Error(), 500)
 		return