diff --git a/src/at/internal/encoding.gleam b/src/at/internal/encoding.gleam
new file mode 100644
index 0000000..7bc7f64
--- /dev/null
+++ b/src/at/internal/encoding.gleam
@@ -0,0 +1,36 @@
+import gleam/json.{type Json}
+import gleam/list
+import gleam/option.{type Option, None, Some}
+import gleam/set
+import gleam/uri
+
+pub fn optional_object(
+  required: List(#(String, Json)),
+  optional: List(Option(#(String, Json))),
+) -> Json {
+  optional
+  |> list.filter_map(option.to_result(_, Error(Nil)))
+  |> list.append(required)
+  |> json.object
+}
+
+pub fn optional_field(
+  name: String,
+  value: Option(a),
+  inner: fn(a) -> Json,
+) -> Option(#(String, Json)) {
+  case value {
+    Some(v) -> Some(#(name, inner(v)))
+    None -> None
+  }
+}
+
+pub fn uri(value: uri.Uri) -> Json {
+  json.string(uri.to_string(value))
+}
+
+pub fn set(value: set.Set(a), inner: fn(a) -> Json) -> Json {
+  json.preprocessed_array(
+    set.fold(value, [], fn(values, v) { [inner(v), ..values] }),
+  )
+}