Currently if you add a field in the fields parameter with a wildcard, no fields will be added to the hits layer. The situation is even worst if the wildcard matches the field name of the geo_point or geo_shape field, in that case a ClassCastException is thrown.
x-pack/plugin/vector-tile/src/javaRestTest/java/org/elasticsearch/xpack/vectortile/VectorTileRestIT.java
assertThat(layer.getFeatures(0).getType(), Matchers.equalTo(VectorTile.Tile.GeomType.POINT));
        }
        {
            final Request mvtRequest = new Request(
                getHttpMethod(),
                INDEX_POINTS + "/_mvt/location/" + z + "/" + x + "/" + y + "?exact_bounds=false"
            );
            mvtRequest.setJsonEntity("{\"size\" : 0, \"grid_precision\" : 0, \"exact_bounds\" : true}");
            final VectorTile.Tile tile = execute(mvtRequest);
            assertThat(tile.getLayersCount(), Matchers.equalTo(1));
            assertLayer(tile, META_LAYER, 4096, 1, 8);
            final VectorTile.Tile.Layer layer = getLayer(tile, META_LAYER);
            assertThat(layer.getFeatures(0).getType(), Matchers.equalTo(VectorTile.Tile.GeomType.POLYGON));
        }
    }
    public void testEmpty() throws Exception {
        final int newY = (1 << z) - 1 == y ? y - 1 : y + 1;
        final Request mvtRequest = new Request(getHttpMethod(), INDEX_POINTS + "/_mvt/location/" + z + "/" + x + "/" + newY);
        final VectorTile.Tile tile = execute(mvtRequest);
        assertThat(tile.getLayersCount(), Matchers.equalTo(1));
        assertLayer(tile, META_LAYER, 4096, 1, 10);
    }
    public void testGridPrecision() throws Exception {
        {
            final Request mvtRequest = new Request(getHttpMethod(), INDEX_POINTS + "/_mvt/location/" + z + "/" + x + "/" + y);
            mvtRequest.setJsonEntity("{\"size\" : 100, \"grid_precision\": 7 }");
            final VectorTile.Tile tile = execute(mvtRequest);
            assertThat(tile.getLayersCount(), Matchers.equalTo(3));
            assertLayer(tile, HITS_LAYER, 4096, 33, 2);