Scripting ImportMetadata_conversion in Python worked for me with ArcGIS Desktop 10.1. Now ImportMetadata_conversion won't run in script; I am now on ArcGIS for Desktop 10.2.2. I get "ERROR 000816: The tool is not valid."
Although problems with scripting metadata processes might not be very significant in some organizations, my organization provides a GIS data clearinghouse. Metadata processing is a significant part of our work.
I was disappointed because the ImportMetadata_conversion Help document in ArcGIS for Desktop did not indicate that the tool won't work in an external script. I wrote a script that uses ImportMetadata_conversion, and then discovered that ImportMetadata_conversion won't run in the script.
