diff --git a/documentation/RELEASE_NOTES.md b/documentation/RELEASE_NOTES.md
index c1914e95f..870be17a4 100644
--- a/documentation/RELEASE_NOTES.md
+++ b/documentation/RELEASE_NOTES.md
@@ -17,6 +17,16 @@ should also be read to understand what has changed since earlier releases.
 
 <!-- Insert new items immediately below here ... -->
 
+### Tab completion for IOC shell
+
+When built with optional libreadline support, the interactive IOC shell will perform tab
+completion for command names as well as some arguments of built-in commands.
+eg. the record name argument of `dbpr`, and the path name argument of `cd`.
+
+Externally defined commands have a limited ability to opt into completion with
+the newly added `iocshArgStringRecord` and `iocshArgStringPath` argument types.
+Both function identically to `iocshArgString` with an added hint about completion.
+
 ### Add FMOD as CALC Expression
 
 The floating point modulo function `FMOD(NUM,DEN)` is added.
diff --git a/modules/libcom/src/iocsh/iocsh.h b/modules/libcom/src/iocsh/iocsh.h
index 70bf9af37..ef0d5c50d 100644
--- a/modules/libcom/src/iocsh/iocsh.h
+++ b/modules/libcom/src/iocsh/iocsh.h
@@ -66,7 +66,13 @@ typedef enum {
     iocshArgPdbbase,
     iocshArgArgv,
     iocshArgPersistentString,
+    /** Equivalent to iocshArgString with a hint for tab completion as a record name.
+     *  @since UNRELEASED
+     */
     iocshArgStringRecord,
+    /** Equivalent to iocshArgString with a hint for tab completion as a file system path.
+     *  @since UNRELEASED
+     */
     iocshArgStringPath,
 }iocshArgType;