diff --git a/gdb/mgodb/bson.go b/gdb/mgodb/bson.go
index 5c9e206..ec8ea50 100644
--- a/gdb/mgodb/bson.go
+++ b/gdb/mgodb/bson.go
@@ -9,5 +9,14 @@ package mgodb
 
 import "go.mongodb.org/mongo-driver/bson"
 
+// M is an unordered representation of a BSON document.
+// bson.M{"foo": "bar", "hello": "world", "pi": 3.14159}
 type M = bson.M
+
+// A D should not be constructed with duplicate key names, as that can cause undefined server behavior.
+// bson.D{{"foo", "bar"}, {"hello", "world"}, {"pi", 3.14159}}
 type D = bson.D
+
+// An A is an ordered representation of a BSON array.
+// bson.A{"bar", "world", 3.14159, bson.D{{"qux", 12345}}}
+type A = bson.A
diff --git a/gdb/mgodb/find.go b/gdb/mgodb/find.go
new file mode 100644
index 0000000..c31bb45
--- /dev/null
+++ b/gdb/mgodb/find.go
@@ -0,0 +1,16 @@
+//
+// find.go
+// Copyright (C) 2023 tiglog <me@tiglog.com>
+//
+// Distributed under terms of the MIT license.
+//
+
+package mgodb
+
+import "go.mongodb.org/mongo-driver/mongo/options"
+
+// Find creates a new FindOptions instance.
+var Find = options.Find
+
+// FindOne creates a new FindOneOptions instance.
+var FindOne = options.FindOne