diff --git a/docs/layers.md b/docs/layers.md
index b9c0d455d..af6d24fed 100644
--- a/docs/layers.md
+++ b/docs/layers.md
@@ -141,8 +141,8 @@ Combination of OpenStreetMap administrative boundaries (zoom >= 8) and Natural E
 
 #### Boundaries properties (common):
 
-* `name`
-* `id`
+* `name`: A suggested label, formed from the left and right region names, if available. If the name appears to be too long to be rendered on the geometry at a particular zoom it may be omitted.
+* `id`: Identifier for the feature, only provided at zoom 13+.
 * `kind`: mapping of OpenStreetMap's `admin_level` int values to strings like `country` and `state`, plus `aboriginal_lands` boundary type, and also includes normalized Natural Earth values.
 * `kind_detail`: mapping of OpenStreetMap's `admin_level` values. `2` for countries, `4` for regions, and `6`, `8` (zoom 10+)
 * `source`: `openstreetmap.org` or `naturalearthdata.com`
@@ -151,8 +151,8 @@ Combination of OpenStreetMap administrative boundaries (zoom >= 8) and Natural E
 
 #### Boundaries properties (common optional):
 
-* `id:left`: For the relation on the left side of the boundary line.
-* `id:right`: For the relation on the right side of the boundary line.
+* `id:left`: For the relation on the left side of the boundary line. This is only provided at zoom 13+.
+* `id:right`: For the relation on the right side of the boundary line. This is only provided at zoom 13+.
 * `name:left`: See name section above, other variants like `old_name` also supported. _See planned bug fix in [#1102](https://github.com/tilezen/vector-datasource/issues/1102)._
 * `name:right`: See name section above, other variants like `old_name` also supported. _See planned bug fix in [#1102](https://github.com/tilezen/vector-datasource/issues/1102)._
 * `maritime_boundary`: a special Tilezen calculated value loosely coupled with OpenStreetMap's maritime tag, but with spatial buffer processing for lines falling in the ocean.
diff --git a/integration-test/1012-sort_key-boundary.py b/integration-test/1012-sort_key-boundary.py
index 3280e6839..e77101525 100644
--- a/integration-test/1012-sort_key-boundary.py
+++ b/integration-test/1012-sort_key-boundary.py
@@ -40,5 +40,5 @@ def test_san_francisco_daly_city_locality_boundary(self):
             'https://www.openstreetmap.org/relation/112271',
         ], clip=self.tile_bbox(10, 163, 396, padding=0.1))
         self.assert_has_feature(
-            10, 163, 396, "boundaries",
+            11, 326, 792, "boundaries",
             {"kind": "locality", "sort_rank": 252})
diff --git a/integration-test/1482-maritime_boundary-buffered_land.py b/integration-test/1482-maritime_boundary-buffered_land.py
index aa88d7f6f..2156c6b65 100644
--- a/integration-test/1482-maritime_boundary-buffered_land.py
+++ b/integration-test/1482-maritime_boundary-buffered_land.py
@@ -75,7 +75,6 @@ def test_generative_non_maritime(self):
 
         self.assert_has_feature(
             z, x, y, 'boundaries', {
-                'id': 2,
                 'kind': 'country',
                 'maritime_boundary': type(None),
             })
@@ -95,7 +94,6 @@ def test_generative_maritime(self):
 
         self.assert_has_feature(
             z, x, y, 'boundaries', {
-                'id': 2,
                 'kind': 'country',
                 'maritime_boundary': True,
             })
diff --git a/integration-test/1715-slimming-down-boundaries.py b/integration-test/1715-slimming-down-boundaries.py
new file mode 100644
index 000000000..8840239f8
--- /dev/null
+++ b/integration-test/1715-slimming-down-boundaries.py
@@ -0,0 +1,72 @@
+# -*- encoding: utf-8 -*-
+from . import FixtureTest
+
+
+class BoundaryIdTest(FixtureTest):
+
+    def _setup(self, z, x, y, left_id, right_id):
+        from tilequeue.tile import coord_to_bounds
+        from shapely.geometry import LineString
+        from ModestMaps.Core import Coordinate
+        import dsl
+
+        minx, miny, maxx, maxy = coord_to_bounds(
+            Coordinate(zoom=z, column=x, row=y))
+
+        # move the coordinate points slightly out of the tile, so that we
+        # don't get borders along the sides of the tile.
+        w = maxx - minx
+        h = maxy - miny
+        minx -= 0.5 * w
+        miny -= 0.5 * h
+        maxx += 0.5 * w
+        maxy += 0.5 * h
+
+        self.generate_fixtures(
+            dsl.way(
+                1,
+                LineString([
+                    [minx, miny],
+                    [minx, maxy],
+                    [maxx, maxy],
+                    [minx, miny],
+                ]), {
+                    'boundary': 'administrative',
+                    'admin_level': '2',
+                    'id': left_id,
+                    'name': 'Left',
+                }
+            ),
+            dsl.way(
+                2,
+                LineString([
+                    [minx, miny],
+                    [maxx, maxy],
+                    [maxx, miny],
+                    [minx, miny],
+                ]), {
+                    'boundary': 'administrative',
+                    'admin_level': '2',
+                    'id': right_id,
+                    'name': 'Right',
+                }
+            ),
+        )
+
+    def test_have_ids_at_z13(self):
+        z, x, y = (13, 100, 100)
+        self._setup(z, x, y, 1, 2)
+        self.assert_has_feature(
+            z, x, y, 'boundaries', {
+                'id:left': 1,
+                'id:right': 2,
+            })
+
+    def test_dropped_at_z12(self):
+        z, x, y = (12, 50, 50)
+        self._setup(z, x, y, 1, 2)
+        self.assert_has_feature(
+            z, x, y, 'boundaries', {
+                'id:left': type(None),
+                'id:right': type(None),
+            })
diff --git a/integration-test/841-normalize-boundaries-kind.py b/integration-test/841-normalize-boundaries-kind.py
index 0405ff92e..ad316eee4 100644
--- a/integration-test/841-normalize-boundaries-kind.py
+++ b/integration-test/841-normalize-boundaries-kind.py
@@ -103,64 +103,64 @@ def test_admin1(self):
         # Admin-1 boundary
         self.assert_has_feature(
             7, 75, 70, 'boundaries',
-            {'id': int, 'kind': 'region', 'kind_detail': '4'})
+            {'kind': 'region', 'kind_detail': '4'})
 
     def test_admin1_statistical(self):
         # Admin-1 statistical boundary
         self.assert_has_feature(
             7, 101, 56, 'boundaries',
-            {'id': int, 'kind': 'region', 'kind_detail': '4'})
+            {'kind': 'region', 'kind_detail': '4'})
 
     def test_admin1_statistical_meta(self):
         # Admin-1 statistical meta bounds
         self.assert_has_feature(
             7, 26, 52, 'boundaries',
-            {'id': int, 'kind': 'region', 'kind_detail': '4'})
+            {'kind': 'region', 'kind_detail': '4'})
 
     def test_admin1_region(self):
         # Admin-1 region boundary
         self.assert_has_feature(
             7, 99, 57, 'boundaries',
-            {'id': int, 'kind': 'macroregion', 'kind_detail': '3'})
+            {'kind': 'macroregion', 'kind_detail': '3'})
 
     def test_disputed(self):
         # Disputed (please verify)
         self.assert_has_feature(
             7, 39, 71, 'boundaries',
-            {'id': int, 'kind': 'disputed', 'kind_detail': '2'})
+            {'kind': 'disputed', 'kind_detail': '2'})
 
     def test_indefinite(self):
         # Indefinite (please verify)
         self.assert_has_feature(
             7, 20, 44, 'boundaries',
-            {'id': int, 'kind': 'indefinite', 'kind_detail': '2'})
+            {'kind': 'indefinite', 'kind_detail': '2'})
 
     def test_indeterminant(self):
         # Indeterminant frontier
         self.assert_has_feature(
             7, 91, 50, 'boundaries',
-            {'id': int, 'kind': 'indeterminate', 'kind_detail': '2'})
+            {'kind': 'indeterminate', 'kind_detail': '2'})
 
     def test_international(self):
         # International boundary (verify)
         self.assert_has_feature(
             7, 67, 37, 'boundaries',
-            {'id': int, 'kind': 'country', 'kind_detail': '2'})
+            {'kind': 'country', 'kind_detail': '2'})
 
     def test_lease_limit(self):
         # Lease limit
         self.assert_has_feature(
             7, 86, 45, 'boundaries',
-            {'id': int, 'kind': 'lease_limit', 'kind_detail': '2'})
+            {'kind': 'lease_limit', 'kind_detail': '2'})
 
     def test_line_of_control(self):
         # Line of control (please verify)
         self.assert_has_feature(
             7, 90, 50, 'boundaries',
-            {'id': int, 'kind': 'line_of_control', 'kind_detail': '2'})
+            {'kind': 'line_of_control', 'kind_detail': '2'})
 
     def test_overlay(self):
         # Overlay limit
         self.assert_has_feature(
             7, 109, 49, 'boundaries',
-            {'id': int, 'kind': 'overlay_limit', 'kind_detail': '2'})
+            {'kind': 'overlay_limit', 'kind_detail': '2'})
diff --git a/integration-test/976-fractional-pois.py b/integration-test/976-fractional-pois.py
index 4f1fb796e..8708cc2c9 100644
--- a/integration-test/976-fractional-pois.py
+++ b/integration-test/976-fractional-pois.py
@@ -92,7 +92,7 @@ def test_boundaries(self):
         # transit, and water
         self.assert_has_feature(
             5, 9, 12, 'boundaries',
-            {'min_zoom': 2, 'id': int,
+            {'min_zoom': 2,
              'source': 'naturalearthdata.com',
              'kind': 'region'})
 
diff --git a/queries.yaml b/queries.yaml
index d9d1501bf..0d46d32ee 100644
--- a/queries.yaml
+++ b/queries.yaml
@@ -602,6 +602,20 @@ post_process:
       base_layer: boundaries
       start_zoom: 8
 
+  # drop id/id:left/id:right on boundaries up to zoom 12 inclusive.
+  # the left/right IDs tend to be unique as a pair, and so prevent merging.
+  # the id itself will be dropped by merging if it's possible to merge, and
+  # at mid and low zooms is of dubious usefulness.
+  - fn: vectordatasource.transform.drop_properties
+    params:
+      source_layer: boundaries
+      start_zoom: 0
+      end_zoom: 13
+      properties:
+        - id
+        - "id:left"
+        - "id:right"
+
   # try to merge boundaries into as long segments as possible.
   - fn: vectordatasource.transform.merge_line_features
     params:
@@ -628,6 +642,14 @@ post_process:
       end_zoom: 7
       properties: [name]
 
+  # after dropping names, try again to merge boundaries into as few features as
+  # possible (to reduce tile size).
+  - fn: vectordatasource.transform.merge_line_features
+    params:
+      source_layer: boundaries
+      start_zoom: 8
+      end_zoom: 15
+
   # before extracting the label placement points, remove small water areas which
   # are probably too small to label.
   - fn: vectordatasource.transform.drop_properties
diff --git a/yaml/boundaries.yaml b/yaml/boundaries.yaml
index d396cde5d..6abb95b5d 100644
--- a/yaml/boundaries.yaml
+++ b/yaml/boundaries.yaml
@@ -83,7 +83,7 @@ filters:
       kind_detail: '6'
     table: osm
   - filter: {admin_level: '8', boundary: administrative}
-    min_zoom: 10
+    min_zoom: 11
     output:
       <<: *output_properties
       kind: locality