Using "-m module" is easier to read and understand than "-mmodule".

Doc/library/json.rst

@@ -97,11 +97,11 @@ Extending :class:`JSONEncoder`::
 
 Using json.tool from the shell to validate and pretty-print::
 
-    $ echo '{"json":"obj"}' | python -mjson.tool
+    $ echo '{"json":"obj"}' | python -m json.tool
     {
         "json": "obj"
     }
-    $ echo '{1.2:3.4}' | python -mjson.tool
+    $ echo '{1.2:3.4}' | python -m json.tool
     Expecting property name enclosed in double quotes: line 1 column 2 (char 1)
 
 .. highlight:: python3