review: add back bbox and note that bbox and geometry are not yet sup…

…ported for filtering

README.md

@@ -945,23 +945,32 @@ not advertise any queryables properties (note the empty `properties` field):
 ### Filter Extension
 
 Stac-server currently implements the Filter Extension such that the `id`, `collection`,
-and `geometry` Item fields and all fields in the `properties` object of an Item are always
-available as filter terms for a Collection, regardless of whether a Collection defines a
-`queryables` field or not. This behavior aligns with a value of `true` for the
+`bbox`, and `geometry` Item fields and all fields in the `properties` object of an Item
+are always available as filter terms for a Collection, regardless of whether a Collection
+defines a `queryables` field or not. This behavior aligns with a value of `true` for the
 `additionalProperties` field in the queryables definition. Stac-server currently
-_requires_ `additionalProperties` to be `true`; a value of `false`, which would restrict
-filtering to only those `properties` defined in a Collection's queryable schema, is not
+**requires** `additionalProperties` to be `true`; a value of `false`, which would restrict
+filtering to only those `properties` defined in a Collection's queryables schema, is not
 supported and will raise an error. Thus, adding a `queryables` field to a Collection is
 informative only - it does not change the behavior of a filter.
 
 Note that when creating a filter expression that uses fields from the `properties` object
 in an Item, the fields **must not** be prefixed, e.g., use `eo:cloud_cover` instead of
 `properties.eo:cloud_cover` in the filter expression. Care must be taken that terms used
-in a filter expression exactly match the field names in the Item `properties` object.
-There is no validation that filter expression terms are correct, so if you search for a
+in a filter expression exactly match the field names in the Item `properties` object;
+there is no validation that filter expression terms are correct, so if you search for a
 field that doesn't exist in an Item's `properties` object, that Item will never be
 matched.
 
+The`id`, `collection`, `bbox`, and `geometry` fields also **must not** be prefixed since
+they are top-level Item fields. Note that until the [Basic Spatial Functions with
+additional Spatial
+Literals](https://docs.ogc.org/is/21-065r2/21-065r2.html#rc_basic-spatial-functions-plus)
+and [Array
+Functions](https://docs.ogc.org/is/21-065r2/21-065r2.html#_conformance_class_array_functions)
+conformance classes are implemented, searching over the `bbox` and `geometry` fields is
+not supported.
+
 ### Query Extension
 
 Unlike the Filter Extension, the Query Extension does not (yet) define a mechanism to