diff --git a/gates/pool.py b/gates/pool.py
index e3e94e4..64bb7ff 100644
--- a/gates/pool.py
+++ b/gates/pool.py
@@ -103,6 +103,14 @@ def resolve_slot(manifest, index_widget):
     return max(0, min(idx, n - 1))
 
 
+def set_label(base_dir, pool_id, index, label):
+    m = read_manifest(base_dir, pool_id)
+    if 0 <= index < len(m["slots"]):
+        m["slots"][index]["label"] = str(label)
+        write_manifest(base_dir, pool_id, m)
+    return m
+
+
 def rebuild_manifest(base_dir, pool_id):
     # Temporary stub — replaced in Task 7.
     return empty_manifest()
diff --git a/tests/test_pool.py b/tests/test_pool.py
index 0edb908..c1539da 100644
--- a/tests/test_pool.py
+++ b/tests/test_pool.py
@@ -85,3 +85,15 @@ def test_resolve_slot_rules():
     assert pool.resolve_slot(m, 0) == 0      # forced
     assert pool.resolve_slot(m, 9) == 2      # clamp high
     assert pool.resolve_slot({"active": 0, "slots": [], "next_seq": 1}, -1) == -1  # empty
+
+
+def test_set_label(tmp_path):
+    pool.add_image(str(tmp_path), "p1", b"a", ts=1)
+    m = pool.set_label(str(tmp_path), "p1", 0, "front view")
+    assert m["slots"][0]["label"] == "front view"
+
+
+def test_set_label_out_of_range_noop(tmp_path):
+    pool.add_image(str(tmp_path), "p1", b"a", ts=1)
+    m = pool.set_label(str(tmp_path), "p1", 5, "x")
+    assert m["slots"][0]["label"] == ""