Looking at an unified API to configuring distributed systems, I've studied various configuration tools.

Most of them define an abstraction services configuration language, more or less linked to the language in which the tool is written itself: Python, Ruby, perl, etc. Configuration recipes can eventually contain some code snippets written in this language, which is not the language of the tool to configure (for instance, Apache). 

Due to the lack of standard configuration language, a really few upstream projects are implied in writing these recipes for every configuration tools. In the best case, they provide for one or two of them. As to offer users the biggest set of turnkey solutions, one can setup recipes repository or good tutorials to ease recipes creation and sharing. But this is always done by the community of the configuration tool, not implying upstream projects. 

It seems that SNMP could a good candidate to describe a configuration API for clouds.

The following page describes why and how SNMP could be used for managing clouds: SNMP4clouds