diff --git a/idl/GCObjectVisitor.json5 b/idl/GCObjectVisitor.json5
index fe6fbb1..07d9973 100644
--- a/idl/GCObjectVisitor.json5
+++ b/idl/GCObjectVisitor.json5
@@ -43,6 +43,7 @@
             doc: [
                 "allocation metadata for gc-aware data at address @p gco.",
                 "@p gco must be the result of a call to collector's alloc() function",
+                "note: load-bearing for xo-gc/MutationLogStore",
             ],
             return_type: "AllocInfo",
             args: [
@@ -57,7 +58,8 @@
             name: "generation_of",
             doc: [
                 "generation to which pointer @p addr belongs, given role @p r;",
-                "sentinel if @p addr is not owned by collector",
+                "sentinel if @p addr is not owned by collector.",
+                "note: load-bearing for xo-gc/MutationLogStore",
             ],
             return_type: "Generation",
             args: [
diff --git a/include/xo/alloc2/gc/AGCObjectVisitor.hpp b/include/xo/alloc2/gc/AGCObjectVisitor.hpp
index 86cd9b9..71a1367 100644
--- a/include/xo/alloc2/gc/AGCObjectVisitor.hpp
+++ b/include/xo/alloc2/gc/AGCObjectVisitor.hpp
@@ -60,10 +60,12 @@ public:
     /** destroy instance @p d; calls c++ dtor only for actual runtime type; does not recover memory **/
     virtual void _drop(Opaque d) const noexcept = 0;
     /** allocation metadata for gc-aware data at address @p gco.
-@p gco must be the result of a call to collector's alloc() function **/
+@p gco must be the result of a call to collector's alloc() function
+note: load-bearing for xo-gc/MutationLogStore **/
     virtual AllocInfo alloc_info(Copaque data, void * addr)  const = 0;
     /** generation to which pointer @p addr belongs, given role @p r;
-sentinel if @p addr is not owned by collector **/
+sentinel if @p addr is not owned by collector.
+note: load-bearing for xo-gc/MutationLogStore **/
     virtual Generation generation_of(Copaque data, Role r, const void * addr)  const  noexcept = 0;
 
     // nonconst methods