diff --git a/src/core/collector.ml b/src/core/collector.ml
index fb7ebbb..180933b 100644
--- a/src/core/collector.ml
+++ b/src/core/collector.ml
@@ -53,10 +53,15 @@ module type S = sig
   (** Exit an explicit span.
       @since 0.3 *)
 
-  val add_data_to_span : span -> (string * user_data) list -> unit
-  (** @since Adds data to the given span.
+  val add_data : (string * user_data) list -> unit
+  (** @since Adds data to the ambient span.
       NEXT_RELEASE *)
 
+  val add_data_to_manual_span :
+    explicit_span -> (string * user_data) list -> unit
+  (** Adds data to the given span.
+      @since NEXT_RELEASE *)
+
   val message : ?span:span -> data:(string * user_data) list -> string -> unit
   (** Emit a message with associated metadata. *)
 
diff --git a/src/core/trace_core.ml b/src/core/trace_core.ml
index 2365e8d..d89ed8c 100644
--- a/src/core/trace_core.ml
+++ b/src/core/trace_core.ml
@@ -55,15 +55,19 @@ let[@inline] exit_manual_span espan : unit =
   | None -> ()
   | Some (module C) -> C.exit_manual_span espan
 
-let[@inline] add_data_to_span (span : span) data : unit =
+let[@inline] add_data data : unit =
   if data <> [] then (
     match A.get collector with
     | None -> ()
-    | Some (module C) -> C.add_data_to_span span data
+    | Some (module C) -> C.add_data data
   )
 
-let[@inline] add_data_to_explicit_span esp data : unit =
-  add_data_to_span esp.span data
+let[@inline] add_data_to_manual_span esp data : unit =
+  if data <> [] then (
+    match A.get collector with
+    | None -> ()
+    | Some (module C) -> C.add_data_to_manual_span esp data
+  )
 
 let message_collector_ (module C : Collector.S) ?span ?(data = fun () -> []) msg
     : unit =
diff --git a/src/core/trace_core.mli b/src/core/trace_core.mli
index 1421a08..ee27b6f 100644
--- a/src/core/trace_core.mli
+++ b/src/core/trace_core.mli
@@ -34,8 +34,9 @@ val with_span :
     see {!enter_manual_span}.
 *)
 
-val add_data_to_span : span -> (string * user_data) list -> unit
-(** Add structured data to the given span.
+val add_data : (string * user_data) list -> unit
+(** Add structured data to the current span (the ambient {!with_span}).
+    Behavior is not specified if there is no current span.
     @since NEXT_RELEASE *)
 
 val enter_manual_sub_span :
@@ -79,10 +80,9 @@ val exit_manual_span : explicit_span -> unit
     {!enter_manual_toplevel_span}.
     @since 0.3 *)
 
-val add_data_to_explicit_span :
-  explicit_span -> (string * user_data) list -> unit
-(** [add_data_explicit esp data] is [add_data_to_span esp.span data], ie. it adds
-    the pairs [k:v] from [data] to the span inside [esp].
+val add_data_to_manual_span : explicit_span -> (string * user_data) list -> unit
+(** [add_data_explicit esp data] adds [data] to the span [esp].
+      The behavior is not specified is the span has been exited already.
     @since NEXT_RELEASE *)
 
 val message :