diff --git a/src/digimarks/main.py b/src/digimarks/main.py
index 93a76d7..65fb0c9 100644
--- a/src/digimarks/main.py
+++ b/src/digimarks/main.py
@@ -288,25 +288,18 @@ async def list_tags_for_user(
     user_key: str,
 ) -> list[str]:
     """List all tags in use by the user."""
-    result = await session.exec(
-        select(Bookmark).where(Bookmark.user_key == user_key, Bookmark.status != Visibility.DELETED)
-    )
-    bookmarks = result.all()
-    tags = []
-    for bookmark in bookmarks:
-        tags += bookmark.tag_list
-    return tags_service.clean_tags(tags)
+    return await tags_service.list_tags_for_user(session, user_key)
 
 
 @app.get('/api/v1/{user_key}/tags/{tag_key}')
 async def list_bookmarks_for_tag_for_user(
     session: SessionDep,
     user_key: str,
+    tag_key: str,
 ) -> list[str]:
     """List all tags in use by the user."""
-    result = await session.exec(select(Bookmark).where(Bookmark.user_key == user_key))
-    bookmarks = result.all()
-    return tags_service.list_tags_for_bookmarks(bookmarks)
+    logger.info('List bookmarks for tag %s user %s', user_key)
+    return await tags_service.list_bookmarks_for_tag_for_user(session, user_key, tag_key)
 
 
 @app.get('/{user_key}', response_class=HTMLResponse)
diff --git a/src/digimarks/tags_service.py b/src/digimarks/tags_service.py
index ad8fca4..d1c766d 100644
--- a/src/digimarks/tags_service.py
+++ b/src/digimarks/tags_service.py
@@ -1,8 +1,9 @@
 """Helper functions for tags used with Bookmark models."""
 
 from sqlalchemy import Sequence
+from sqlmodel import select
 
-from src.digimarks.models import Bookmark
+from src.digimarks.models import Bookmark, Visibility
 
 
 def i_filter_false(predicate, iterable):
@@ -56,7 +57,7 @@ def list_tags_for_bookmarks(bookmarks: Sequence[Bookmark]) -> list[str]:
     """Generate a unique list of the tags from the list of bookmarks."""
     tags = []
     for bookmark in bookmarks:
-        tags += bookmark.tags_list
+        tags += bookmark.tag_list
     return clean_tags(tags)
 
 
@@ -69,3 +70,30 @@ def set_tags(bookmark: Bookmark, new_tags: str) -> None:
     tags_split = new_tags.split(',')
     tags_clean = clean_tags(tags_split)
     bookmark.tags = ','.join(tags_clean)
+
+
+async def list_tags_for_user(
+    session,
+    user_key: str,
+) -> list[str]:
+    """List all tags in use by the user."""
+    result = await session.exec(
+        select(Bookmark).where(Bookmark.user_key == user_key, Bookmark.status != Visibility.DELETED)
+    )
+    bookmarks = result.all()
+    tags = []
+    for bookmark in bookmarks:
+        tags += bookmark.tag_list
+    return clean_tags(tags)
+
+
+async def list_bookmarks_for_tag_for_user(
+    session,
+    user_key: str,
+    tag_key: str,
+) -> list[str]:
+    """List all tags in use by the user."""
+    result = await session.exec(select(Bookmark).where(Bookmark.user_key == user_key))
+    # TODO: filter on tag_key
+    bookmarks = result.all()
+    return list_tags_for_bookmarks(bookmarks)