described required format of metadata for recording_metakeys table

README.md

@@ -1304,7 +1304,9 @@ Optionally included keys are:
 * `metadata`
 
 	This is a generic metadata string. The metadata will be written to the bottom of
-	metadata files within `/path/to/recording_dir/metadata/`. This can be used to
+	metadata files within `/path/to/recording_dir/metadata/` or to
+	`recording_metakeys` table.  In the latter case, metadata needs to
+	be a list of `key:val` pairs separated by `|` character.  `metadata` can be used to
 	record additional information about recorded calls. `metadata` values passed in
 	through subsequent messages will overwrite previous metadata values.