[galaxy-dev] Determining galaxy api path automatically from a tool via dynamic_options?

After uploading my beta status tool to our test toolshed, I tried installing it on another of our galaxy servers but it wasn't able to find the api endpoint url. Is there a way to automatically do this within tool forms? I was hoping to avoid hardcoding this as part of the tool installation process. I'd thought I had it automated: In tool's form, a dynamic_options param <param name="api_url" display="radio" type="drill_down" label="For user with Galaxy API Key" dynamic_options="vdb_init_tool_user(__trans__)" /> was able to pass "trans" galaxy structure so I got as far as this python: self.api_url = 'http://' + trans.request.host ... but this yeilds http://acme.com/ rather than what's needed, the path to a particular installation: http://acme.com/galaxy/ I couldn't find a way to read the /galaxylab/ setting from the (slightly dated) universe_wsgi.ini config file - without say reading the file and parsing it. Is there an __app__.config.prefix or somesuch variable where this info is? Thanks! Damion