This presentation describes the Credential Transparency Description Language (CTDL) --an RDF schema-- and a set of open source applications intended to support rich description of credentials througout the credentialing ecosystem. The metadata infrastructure enabled by the CTDL and the open-licensed software will continuously capture, connect, archive and share metadata about credentials, credentialing organizations, quality assurance organizations, competency frameworks, and additional metadata as needed to support an open applications marketplace. The presentation includes a review of the CTDL resources and development processes and will demonstrate how the CTDL schema is used for publishing RDF metadata to the Credential Engine Registry (CER), how an application profile of the CTDL is used by the CER to validate the quality of incoming metadata, and how the open application marketplace can evolve by demonstrating the Workit Search App prototype that consumes metadata from the CER. The presentation will include discussion of the planned development of CTDL-Lite as a markup extension to schema.org.